My Little Sister Is the Best F*p Material - Volume 7 Chapter 06: Miyu and Yamamoto-san

Volume 7 Chapter 06: Miyu and Yamamoto-san

Things should be viewed from multiple angles. Just because her methods defy common ethics doesn’t mean Miyu isn’t helping me. Without her, I’d have hurt Yamamoto-san and distanced myself. Her support lets me believe there’s a path where everyone can be happy. This whole situation stems from my body needing Miyu as my “material” to get off, so I’m not just a collaborator—I’m a central participant.

It might not be that hard. For Miyu, being chosen by me is her happiness. As long as I ensure that, her joy is secured. With that in mind, I want to build a relationship—or memories—with Yamamoto-san so that when I choose Miyu, she can send me off with a smile.

I mulled this over, staring at the ceiling.

(Ugh, can’t move…)

Lying flat, I couldn’t even lift an arm. My fingers barely bent, but the rest felt like I was under full-body anesthesia. The price of pushing past my physical limits with Yamamoto-san yesterday was steeper than I’d imagined.

“Knock knock! Onii-chan, you awake?”

The culprit—my little sister—entered my room. Since childhood, she’s always verbalized her knocks. A quirk, I guess.

“I’m awake.”

“Oh, really?”

She peeked through the door, her hair in a single braid, already dressed to go out.

I crashed right after getting home yesterday and can’t check the time, so I don’t know how long I slept. I barely talked to Miyu. Seeing my exhausted state, she seemed to guess what happened.

“Wait, Miyu, you’re going out?”

“Not right this second, but I’m heading to Haruka’s.”

That’s bad. Really bad. I’m completely immobile. Food’s one thing, but the bathroom’s a crisis.

“My body below the neck won’t budge.”

“Oh, dear.”

Not oh, dear, little sister. If you leave, my room’s doomed.

“Not even a little?”

She knelt beside me, her frilly, busty outfit—her sweet style for meeting Haruka—filling my vision, making my heart race.

“Standing’s impossible, even trying hard.”

“Wow. Should we stick a tube in your dick?”

“Can’t you think of something gentler…?”

Since I’ve been on hold with her, Miyu’s had fewer chances for physical closeness, so she’s been in dry mode lately. I like this side of her too, though.

“Really can’t move?”

“Nope.”

“Even if I said you could do whatever you want with my boobs right now?”

“That’s a cruel question.”

She rested her soft breasts on the bed’s edge, swaying them up and down in front of me. So close I could grab them, yet my powerlessness was maddening.

“Whoa, you can’t move anything?”

“That’s what I’m saying.”

Finally getting it, I pleaded with my eyes for some help.

“When you’re this helpless, it makes me wanna mess with you.”

“I don’t know what that means, but what’re you planning?”

Being pranked by Miyu is a first—scary but exciting.

“Well, it’s naughty.”

As expected, she stood gracefully, slipped her hands under her skirt, and removed her panties. Dangling from her finger was a cute pink pair with a tiny ribbon.

“No way you’re giving me those if I grab them.”

“Didn’t think of that, but… you still want these?”

She looked down at me, not quite with disdain. Yes, Onii-chan wants those panties. Hand them over.

“I won’t get mad if you lift my skirt now.”

“For real!?”

The shock made me yell, followed by a scream from the stabbing pain in my abs. After all her resistance to showing her pussy, to offer it in broad daylight—maybe once in a lifetime.

“Even for your brother, that’s bold… I’m doing it for real…”

“Go ahead. I’ve got time before I leave, so I’ll play with you, Onii-chan.”

She flaunted her skirt, fanning air to tease without revealing anything. Her deadpan taunting exuded confidence, infuriating yet humbling—a brazen little sister. I had to assert my brotherly authority.

But part of me wondered: what kind of brother bets his life on flipping his sister’s skirt?

“If you lift it, you can lick it too.”

“What…!!”

Whispering with a hand to her mouth, her outrageous offer made me throw everything aside, sending pulses to every nerve.

“Uoo… oooh… igh, aah, hurts, hurts… won’t budge…!!”

No matter the commands, only pain returned. My stamina gave out, and I sank back into the bed. One part below was lively, though.

“That part’s moving.”

“It’s a reflex,” I said.

If there’d been time, I’d have begged for sex, but in this state, Miyu would need to take the lead, so she’d likely refuse anyway. After all that with Yamamoto-san yesterday, what am I even thinking?

“If I could move, would you have let me lick you?”

She’s always stubbornly refused oral. No way she’d allow it so easily.

“It’s my time of the month anyway.”

Right. Completely fooled.

“If it wasn’t, would you have let me?”

“I’d have kept my promise, but I’d probably start hating you a little each day.”

“You hate being licked that much…?”

“Even if you were dying tomorrow, I’d say no.”

Miyu nonchalantly slipped her panties back on, then glanced at me with a hint of guilt.

“Well… maybe if you were about to die, I’d let you.”

“So I have to die to get a taste.”

I’m not sure if that counts as kindness, but it felt like a glimpse of her warmth.

“Those are pretty cute panties for period ones. Was it okay to take them off?”

“These are custom, a gift from Haruka. Blood doesn’t flow constantly, so it’s fine. I’m pretty good at controlling it.”

Is that how it works? Women’s bodies are a mystery. If she can control it, maybe I could’ve licked her, but there seem to be more secrets I don’t know, so I dropped it.

“By the way, the bathroom issue’s still unsolved.”

“Oh, right. Should we call Kanade-san? She’d probably jump at the chance to take care of you.”

“She’s not that free…”

Miyu texted her, and Kanade replied, “Okay! Be there soon!” So, Yamamoto-san was coming.

“Is that okay? Inviting her to my room?”

“Things happened.”

Miyu fiddled with her phone, unperturbed. She’s said she hates me being touched by others since we became lovers, so what’s this about? Is Yamamoto-san an exception?

“Yamamoto-san said fighting over me is a competition with you. When did that start?”

“She said that? I haven’t heard anything.”

“But yesterday, she definitely…”

She did say it. Even claimed if I wanted to be with her, it’d happen. A competition like that wouldn’t start without a word.

“It could be seen that way, I guess? Since I’m egging you on, it’d be unfair to say ‘never mind, I’m keeping him’ if you two fell for each other, right?”

“Yeah.”

So, it’s not a formal competition but Miyu’s resolve naturally shaping it into one. Yamamoto-san didn’t outright call it a contest either.

“Still, I don’t think that’ll happen for a second.”

“You can trust me on that.”

It’s about Miyu taking responsibility if her plan fails. She doesn’t expect failure, so she doesn’t see it as a competition.

“For me, I just want Kanade-san to get serious.”

“So if she goes all out, she’ll be satisfied?”

That’s what Yamamoto-san and I thought. Otherwise, there’s no reason for Miyu to let us get so close.

“That’s close, but the nuance is off.”

Miyu sat seiza, leveling her eyes with mine.

“Kanade-san’s like a perfect superhuman, but usually comes off as ditzy or clumsy, right?”

“True. Serious Yamamoto-san is intense, though.”

“That’s the key.”

Miyu leaned in eagerly.

“Because of past trauma, she tries to be a normal high school girl. But being the best at everything, she lives by ‘I could do it if I tried.’”

That aligns with what Kawafuji said, and when Yamamoto-san confided in me in the archive room, she cursed her exceptional body, saying she just wanted a normal life.

“So you called her arrogant.”

Miyu nodded as the pieces connected in my head. I’d been swayed by her saintly side, but thinking back, she was a savvy, charming beauty who knew her appeal.

“To her, you were a rare person who wasn’t interested, the only guy to reject her before dating, and now her first love, so smitten she can’t let go… Well, I made her that way.”

Of course. Miyu drove that gentle Yamamoto-san to obsession, validating her actions. Even if Yamamoto-san saw the trap, she didn’t expect to fall this deep.

“Basically, I don’t want her to see you as ‘someone I could’ve had if I tried,’ even if she steps back. If things end half-baked, it’ll leave regrets in you too. I want to eliminate all that.”

What audacity from my sister—perfectionism or OCD? She once said this plan was to be carefree with me, and that hasn’t changed.

“So I’m making her get serious, then crushing her completely.”

Her eyes narrowed, voice low and resolute. I thought she’d moved past monopolizing me, but her possessiveness was colossal.

Miyu never believed my closeness with Yamamoto-san would satisfy her love. Knowing only defeating a fully committed Yamamoto-san would bring her peace, Miyu lent me to her to draw that out.

“And…”

Miyu paused, locking eyes with me.

“We need as many people as possible to bless us.”

Her cryptic words confirmed the vague reconciliation I’d sensed with Yamamoto-san. Like with Yuka or repaying Haruka, Miyu refuses fleeting goodbyes, no matter how greedy that wish is. She makes it happen. These past months taught me that. My role as a participant might lie there.

“In terms of winning, yesterday settled things pretty clearly.”

My task is to part with Yamamoto-san amicably. I should focus on that.

“Exactly. Most of it’s done.”

Miyu mimed scissors with her fingers, signaling completion.

As expected, it was Miyu’s plan. But Yamamoto-san seemed to have some fight left. Miyu mentioned unresolved issues—maybe what she just said? It didn’t feel like it. Or is it something even she doesn’t realize?

“Oh, Kanade-san’s here.”

Miyu’s phone buzzed, a notification lighting up the screen. Yamamoto-san had arrived, and Miyu went to greet her at the door.

Yamamoto-san, in my room? I’m oddly nervous.

“Hey, Sotomichi-kun, been since yesterday.”

She waved as she entered, her familiar figure strangely out of place in my room. Having a girl over isn’t common for me. Sachiko and Yuka have been here, so now every girl I’ve been involved with has visited my room.

“As you can see, I’m a total fish out of water.”

Miyu gestured palm-up, explaining my state.

“Quite the tuna.”

Yamamoto-san, in a mature off-shoulder knit outfit, brushed her hair back and peered at me. Stared at by two beauties, my immobile body stiffened further.

“So, what exactly should I do?”

“Everything Onii-chan needs, I guess.”

“Got it.”

Is that okay? I mentally quipped as Yamamoto-san leaned in, whispering, “Shall we continue our last study session?” Miyu left for Haruka’s, leaving me alone with her.

“Can I even study like this?”

“We’ll figure it out.”

With Yamamoto-san carrying me to the toilet, that crisis was averted. Back in bed, I faced her “lesson.” She pulled out a kanji workbook and sat beside me.

“My arms don’t move.”

“I’ll write. You read.”

“Oh? Write where?”

“On your chest… or around your navel… with my finger…”

Of course, she’s the erotic teacher.

“No, I’m not planning to get naughty today. You don’t seem up for it, and doing that here feels wrong to Miyu-chan.”

Fair consideration.

“I’m left high and dry, though…”

“Well, you can get it out with the right person later.”

“True.”

The joy of having someone to relieve me—I can’t take it for granted. Months ago, I’d have killed for this.

“…This is sudden, but…”

She set the book down, speaking softly.

“You and Miyu-chan really do that, right?”

“Y-Yeah.”

I got her point. Hearing about it is one thing, but imagining real siblings getting it on in this bed is tough. Especially since she was just chatting with Miyu, and now I’m here. Even with friends, knowing they’re hooking up makes you look away.

“That’s… wild…”

She blushed faintly. She was the most shocked when I told her Miyu gets me off. Miyu’s peers’ sex lives are abnormal; this is the normal reaction. That unease might make her hesitant now.

“Oh… are you hungry?”

“Yeah, I usually eat breakfast. Might need something.”

“I’ll whip up something special.”

She left the room lightly. Did she want to cook together? Am I overthinking?

She fed me, and as promised, we studied without sex. I pondered what I could do for Miyu’s plan but concluded being myself with Yamamoto-san was best, enjoying our usual banter.

Miyu said we need many to bless us, so staying true to my feelings for Yamamoto-san felt crucial. It aligns with Miyu’s instructions, but understanding its meaning is progress.

“Sotomichi-kun, your arms really don’t move?”

After some light touching during study, she asked, noting I hadn’t even rolled over.

“They might, but it’s like thin branches are stabbing me—weird pain and fear.”

“Got it. How about a massage?”

She lifted my arm onto the blanket, gently kneading from shoulder to fingertips. Massages aren’t ideal for muscle soreness, but my issue seemed beyond that, and her touch helped.

“It hurt at first, but it’s much better.”

My arms became movable. Seeing this, she moved to my legs.

“Uah…!?”

When she pressed my thigh, searing pain shot through me. My arms had supported her waist, but my legs and abs, overworked, were wrecked.

“Legs are still tough, huh.”

She gave up on them but cheerfully grabbed the workbook.

“At least your arms work. You can write now.”

Leaning on the bed’s edge, she pressed her knit-framed breasts against my arm.

“Wanna practice kanji on my boobs?”

She’s always thinking naughty.

“Wicked teacher…”

Her invitation made my lower half twitch. Maybe I should ask for a quick release before Miyu returns.

“Ei!”

“Guh!?”

She jumped onto me, and for twenty seconds, I couldn’t breathe. Her weight—far heavier than she looks—was unlike Miyu’s. The impact forced out all my air, and I felt my organs shift. I thought I’d die.

“No need to overreact.”

She cleared her throat, embarrassed. I could’ve broken ribs, you know.

“Just in case, I brought a water-based marker.”

She handed me a pen labeled “water-based.” What scenario did she envision?

“This might be easier to write on.”

She lifted her shirt to her underbust, revealing smooth, taut skin with just enough fat—perfect for writing.

“Oh?”

Twisting, she eyed something below with interest.

“This guy’s lively as ever.”

Poking my pants, she made the rod’s shape stand out.

“I like it small, but I definitely prefer it big,” Yamamoto-san said with a carefree smile, sparking both joy and a surge of lust in me.

“Sex is still banned today, right?”

“Does that mean you want me to get you off?”

She wasn’t wrong.

“It’s not exactly banned, but… what if Miyu-chan comes back suddenly?”

She seemed worried about being caught mid-act and what might follow.

“That’s fine. Miyu’s the type to be considerate about that.”

“She’s really trusted, huh.”

Yamamoto-san murmured, eyes lowered. The slight oddness in her tone wasn’t my imagination.

“So, kanji practice on your stomach?”

It’s a wildly erotic study method, but for motivation, it’s genius. Is this already a common technique? Nah, no way.

“Here’s the thing—I realized this position has a flaw.”

She traced her breasts’ curves, then slid her hands down her slim waist.

“My boobs block the view, so I can’t see what you write.”

“Then it’s useless…”

She brought a water-based marker but didn’t test this setup?

“But if I take off my top, I can lift my boobs like blinds to peek.”

So she rehearsed naked. Good job, Yamamoto-san. She’s got a Miyu-like vibe now.

“Strip?”

“Shall I?”

I couldn’t resist the temptation. I love her bra-supported breasts, but the slightly flattened shape under gravity is irresistible too.

“Wanna try writing something?”

She arched her back, tautening her stomach. The sight alone was erotic—she’s unfair. Looking up, her twin peaks stood out, a view I never tire of. My erection was painfully intense, and despite the guilt, I started writing “I want a blowjob.”

Meant as a joke, but seeing “blowjob” in bold black on her skin sent a shiver of regret and arousal through me.

“Sotomichi-kun…”

She knew what I wrote without checking, glaring at me sultrily.

“You’re not here to study, are you?”

“Well, it’d be a waste to only study, right?”

“Ugh, you’re hopeless.”

Leaning forward, she pinned my arms with her knees, dangling her massive breasts. So big. And they smell amazing.

“What are you…?”

“You’re thinking naughty thoughts, so I wanna punish—or tease—you a bit.”

Are all girls like this?

“Hehe, you only get to suck these for now, come on!”

“Uoh… ooo…!!”

Whipping my screaming abs, I strained for the reward just out of reach. Every muscle felt like it’d tear, but I didn’t budge a millimeter, collapsing in pathetic defeat. My neck might’ve stretched a bit in these few minutes.

“You’re so cute trying so hard.”

“Ugh…”

I repeated the same failure as with Miyu. But I can’t help it. Even having tasted them before, no man could resist sucking those huge breasts dangled before him.

“Fine, I’ll give you that blowjob you want.”

As expected, she was all in for sex. Facing the opposite way, she lowered her ass near my face, getting on all fours. Those plump, erotic thighs—I want to scribble on them.

“Thinking dirty again?”

She pressed her breasts with her arms, peering at my face between her legs.

“N-No, just… remembering a scene from old AVs.”

Catching my vague hint, she pondered for a moment.

“Wanna write ‘sow’ or something?”

“Not on you, Yamamoto-san…”

Has she seen those kinds of videos?

“For you, ‘free creampie’ would do.”

Her mischievous whisper was tantalizingly sincere.

“Or tally every time we’ve had sex with marks.”

“You have seen hardcore AVs, haven’t you?”

“Unlike you, I study diligently.”

Watching porn to please men? Her dedication is admirable.

“Anyway, shall I get you off?”

She stripped my pants and dove onto my erect cock without hesitation.

“Oh… oof…!”

It’s the best. A blowjob feels amazing—the warmth of her mouth, the sticky saliva, the soft lips and tongue, and above all, a girl working to please a man’s cock, satisfying my dominance.

“Fu… nju… guju…”

“Ahh… so good, Yamamoto-san… you’re amazing…”

I ended up getting sex after all. Yesterday, she jokingly offered to “deliver” herself, and here we are. A gorgeous delivery girl offering free oral and creampies. Realizing I’m about to give up this ultimate male paradise underscores the weight of my choice.

“Hamu… chu… nn, nnh…!”

I reached out, groping her breasts. Unlike Miyu, she doesn’t mind unprompted touching—another perk. Her boobs are so big, I can’t always see her sucking me. But with only my arms working, their weight strained my wrists.

“Ahh… Yamamoto-san… incredible… feels so good…!”

Watching her suck while feeling her soft breasts, occasionally teasing her nipples to draw sexy moans, I savored her reactions. When my arms tired, I traced her thighs, my arousal spiking as she kept sucking despite her pleasure.

“Chu, chupu… juru… nku… jubu…”

“Yamamoto-san, I’m… gonna come…!”

On this bed, in this position, I’d done naughty things with Miyu. That memory made her an easy fantasy.

“Yamamoto-san… coming…!!”

I unleashed the semen pooled in my balls into her mouth. No matter how often, this bliss never fades.

“Nn… kuh… phew. I managed to swallow today,” Yamamoto-san said, flashing a bright smile and a peace sign. She’d been deeply upset about not being able to swallow my semen yesterday. For me, I want her to keep doing it—not just for my satisfaction but because I have a personal wish for her to be that kind of girl.

“Feeling good now, Sotomichi-kun?”

She seemed satisfied with the sex, and we spent the remaining time chatting idly.

When Miyu texted she was returning, I thought Yamamoto-san would leave, but instead, she went to greet Miyu at the door.

What’s it like to sleep with a guy who has a girlfriend and then welcome that girlfriend? Well, I pushed for it.

“I’m back, Onii-chan.”

Miyu returned in the same outfit, with Yamamoto-san trailing behind.

Two gorgeous girls in my room again. With my arms now somewhat functional, I managed to prop myself against the wall by the bed.

“You’ve recovered a lot,” Miyu noted.

“Still pretty rough, though. I’ll need a few days’ rest at home.”

“Thanks for everything, Kanade-san,” Miyu said.

“No problem, it was really fun,” Yamamoto-san replied.

The three of us, in harmony. I hope we can stay close like this as adults.

Yamamoto-san got ready to leave, no plans for dinner together. That’d feel like crossing a line, which I get.

“By the way, about that thing we talked about,” Yamamoto-san said to Miyu. “My chest grew suddenly too, so I might have barely used bras at home. My underbust back then might fit you.”

A sudden topic. What’s this about?

“Uh, well, it’s not decided yet,” Miyu stammered, visibly flustered. No way—Miyu?

“Anyway, it’s dark out, so be careful going home, Kanade-san,” Miyu said, abruptly cutting off the conversation and seeing her out. Was it about breasts swelling during periods?

Speaking of, her period ends in a few days. Then I can do it raw with Miyu. Creampie—will that be okay? Will she set conditions? Should I carry condoms just in case?

“Onii-chan.”

Miyu returned after seeing Yamamoto-san off.

“Oh, Miyu.”

“Lost in thought?”

“Nah, about the date—aquarium and hot springs. When’s good?”

The aquarium’s fine, but hot springs aren’t great during her period, so she’d need to pick the date.

“Three days from now should be fine. Let’s go then.”

“Deal.”

Finally, a date with Miyu is set. Weather won’t matter—three days from now, it’s happening.

“One more thing, just to confirm.”

“What’s that?”

“About, uh, the pill instead of condoms.”

“Go on,” she said, listening calmly.

“If I want to finish inside, what should I do?”

I decided to ask directly, no beating around the bush.

“As long as it’s not in public, do whatever you want.”

“Huh? Oh, okay.”

She tilted her head, genuinely puzzled by my hesitation. Compared to before, these conditions are lax. Creampies are fine, but licking her down there is a hard no? Typical Miyu, I suppose.

“Hm? Why’s that pen there?”

She pointed at the water-based marker I’d left tucked in my pillow.

“Oh, we used it for studying with Yamamoto-san.”

Though we didn’t actually study.

“Hmm.”

She seemed uninterested. Unlike Yamamoto-san, who’d gleefully play along, there’s something thrilling about tainting a stubborn girl like Miyu.

“When we do it raw someday, I kinda want to write ‘Creampie OK’ on your thighs.”

With an arrow.

“Onii-chan, give me the pen.”

She held out her hand, and I placed the marker in it. I knew saying that would piss her off, but my chat with Yamamoto-san got me carried away.

“Wait, that kind of thing doesn’t look good on a guy…!”

How many times have I told Miyu to wait? Today, I ended up bearing the humiliation meant for beautiful girls. Stripped naked, my lower body was scrawled with “Pervert,” “Siscon,” “Cumbrain,” and more, then left there for a while.