S-Rank Adventurer Betrayed by His Fiancée in the Hero’s Party Sets Off on a Journey to Heal His Broken Heart ~The Strongest Betrayed Adventurer Ends Up Forming a Harem Party~ - Chapter 01: Betrayal in the Name of Infidelity

Chapter 01: Betrayal in the Name of Infidelity

It felt like a bad dream. That’s what I thought.

Seeing my beloved fiancée for the first time in three years, with that ecstatic smile on her face.

But she wasn’t looking at me. She was kissing another man… the Hero.

For 14 years, I had spent almost my entire life with her, living for her.

Where did I go wrong?

I tried so hard. I gave it my all. 

What was the point of it all?

These thoughts swirled endlessly in my head, until finally, I—Abel Sixam—sank into the darkness along with my consciousness.

[Side: Adventurer]

“So loud and grand, as expected from the Hero’s triumphant return.”

The Demon King, who had threatened the world, was defeated. Humanity had won the war for its survival!

That’s what everyone was shouting, while clinking their mugs together in celebration. As I walked among them, I—Abel Sixam—muttered to myself.

In my casual clothes, with four swords strapped to my waist, I walked the streets of the royal capital like any other adventurer. My grumbling was easily drowned out in the noise.

The Demon King, who had existed for about two hundred years and sought to rule the world by controlling countless magical beasts, was defeated by the Hero’s Party, led by a Hero summoned from another world.

That happened just about a month ago.

The celebration of the Hero Party’s return, known as the “Hero Festival,” had been going strong for three days now, with no signs of stopping. The people around me continued to drink, sing, and shout in celebration.

I understood how they felt. I wanted to shout, run, and dance, too.

After all… I was finally going to see my fiancée, who had been part of the Hero’s Party.

“Millia… finally.”

After three long years, I was finally going to see her again—my beloved Millia Xelei, my childhood friend from the same village, the one I had promised to marry.

“Finally… finally. Three years since then, and it’s over now…!”

I muttered the words to myself, savoring each one.

It had all started with something small.

During the “Job” evaluation, which determined everyone’s unique skills and magical abilities, we were separated. We had been adventuring together, but that day changed everything.

Millia’s job was “Sage,” said to be the role of a legendary mage. That was the beginning of it all.

Under orders from the kingdom, Millia was summoned to join the Hero’s Demon King Subjugation Party. The Hero had been called from another world.

I wanted to go with her. Even if not as an official member, I didn’t care if I was just doing chores—I just wanted to stay by her side.

But… my job was a simple “Swordsman,” someone who could wield a sword but didn’t possess any special abilities.

Compared to Millia, the Sage, and the exceptional members of the Hero’s Party, I was too ordinary.

At first, I cursed fate. Why did this have to happen to us?

I cursed it, cried, and felt bitter. So much bitterness that it hurt. But that’s why we made a vow.

Millia swore she’d come back alive. And I swore to support her however I could.

When the day came that the Demon King was defeated and we reunited, we would finally be together… that was our special vow.

And now, three years later, the Demon King had been defeated!

“Millia’s magic really is the best! I knew she could do it!”

She had been talented enough to get into the royal capital’s magic academy even before she became an adult. I couldn’t help but smile at my childhood friend’s talent.

“Hey, Abel! What are you wandering around by yourself for? Come over here and drink with us!”

As I walked down the streets of the royal capital, a familiar middle-aged man called out to me, holding a mug as large as a barrel in one hand.

He was the owner of the tool shop I frequented. The old guy had been drinking late into the night yesterday, and now he was at it again.

“Sorry, I’ll pass! Haven’t you been drinking all day, old man? You should take it easy!”

“Ah, let me be! At least on a day like this! You’re no fun!”

“Hey, idiot! You don’t invite the S-Rank adventurer to drink at some shabby place! You know better places, right?”

Another man chimed in, talking to the old shopkeeper.

S-Rank adventurer, huh.

It was a title I had earned without realizing it while working hard for Millia.

Only 11 people in the world held that rank. To other adventurers, I was a living legend. Back in the day, Millia and I used to talk about those legendary S-Rank adventurers, eyes shining with excitement.

Honestly, I still couldn’t believe I had become one of them.

I’m probably the only adventurer who reached S-Rank just for the sake of his lover. What a love-obsessed fool.

“Meeting that sweet girl of yours, Abel?”

“If only! Damn it!”

Messing around with a legend, huh? The people of the royal capital sure have guts!

I’ve never openly declared that I’m dating Millia from the Hero’s Party.

But those who know, know. It’s not like I’ve been hiding it either—people hear me saying things like “I’m working hard for my lover” all the time.

Especially here in the capital, where we made our home up until three years ago. A lot of people still remember how we used to be back then.

“Yeah-Yeah! You’re too busy with a heartwarming reunion with your lover to waste time drinking with us!”

“Whistle~! What a ladies’ man!”

“Shut up! And don’t drink too much!”

I shook my head at the rowdy drunks enjoying themselves as I made my way towards a certain church.

It had been three days since the Hero’s Party returned, and I still hadn’t seen Millia.

On the first day, she had to rest and meet with the king.

The next day was a parade and a party with the nobles.

Today, there was another party with the politicians of the kingdom of Sildiel.

She was busy, so I didn’t make any moves to contact her. 

She’d probably be free by tonight, and if not, there’d be a chance to see her tomorrow. 

As an S-Rank adventurer and her greatest supporter, I was invited to tomorrow’s party.

Still, I couldn’t wait. Maybe I’d get to see her tonight.

I couldn’t help but pick up my pace.

・・・・・

Soon, I arrived at a certain church. It was a quiet place, bathed in moonlight, away from all the noise.

“This brings back memories… I guess this is where it all started.”

This was the church where we came for our Job evaluations—the place of both our beginnings and our separation.

We had promised to meet here again someday, each walking our own paths until then. I took a deep breath. The air was cool and refreshing.

Slowly, I made my way towards the front doors of the church.

—That’s when I heard it. Just as I approached the slightly ajar door, a woman’s voice came through the crack.

It was a voice I remembered vividly, a sweet soprano.

Millia! There was no mistake…!

Unable to contain my excitement, I reached for the doorknob—then froze. Through the small gap in the door, I saw it.

The lover I had longed to see was kissing another man.

“M-Millia…?”

Her chestnut hair, her sharp, confident eyes. 

Her body had grown more mature, with soft curves that made her more beautiful and womanly than I remembered.

She had become even more stunning in these three years… And there she was, kissing someone passionately, their tongues intertwined.

There was no doubt. The woman I was looking at was Millia Xelei.

“Mmm, Yuto…”

“You’re so beautiful, Millia.”

I recognized the man’s face. I’d seen him in the newspapers. His black hair and eyes were distinctive, his unusual name marking him as someone from another world.

That man was Yuto Amano—the Hero.

“Hehe, I’m happy. But from tomorrow, we’ll have fewer chances like this.”

“That’s just how it is. After all, we both have other people in our lives.”

The Hero slid his hand around Millia’s slim waist, letting it roam over her ample hips. Millia didn’t seem to mind at all.

They were talking… like lovers.

Lovers—with someone else but me?

“I can’t be with you completely, but I still love you.”

—What…?

“Even though we each have someone else, my feelings for you won’t change. And we’ll still share plenty of passionate nights!”

“Oh, stop it, you’re such a tease!”

I wasn’t so naïve that I couldn’t understand why they were kissing. Or what they were talking about.

From the conversation alone, it was clear they were involved—not just emotionally, but physically.

In other words, they… she…

“Millia… was cheating on me?”

As soon as I said the words, I felt all the strength drain from my body.

It was as if the ground beneath me was crumbling away, dragging me down into an endless pit.

My mind… was shattering.

“But as much as I hate to leave, we should stop here. I need to go find my fiancé soon…”

“Your ‘old lover’ is just some adventurer, right? He can’t be better than me… Hey, why don’t we head to a nearby inn? I’ll use a potion again and make you pass out from pleasure.”

“Don’t say that! You’re the Hero, and he’s just… well, there’s no comparison. But still, technically, he’s still my fiancé.”

—The two continued talking.

The content… it was all about belittling me.

Millia… was she always the kind of person who said such things? Did she ever have that kind of expression on her face?

These thoughts kept swirling around in my head.

She hadn’t forgotten me. I couldn’t even make that convenient excuse. If she had forgotten me, maybe that would’ve been easier to bear.

(She remembered me, and still cheated…)

I had supported her all this time.

What were these past three years I spent working for the Hero’s Party for?

All that time, I was being betrayed. What a joke.

No, maybe… even the 14 years we spent together…?

“From the moment I became aware of the world, I was always with Millia… I lived for her.”

Through the jumble of my thoughts, I came to a conclusion.

“So that’s it—my life… was meaningless.”

With hands drained of strength, I pushed the slightly open door.

Creak.

“!? What the—!?”

The sound of the wood creaking echoed, and Millia and the Hero, Yuto, turned around.

They spotted me and looked somewhat relieved.

“Ahem. You know, eavesdropping is in poor taste. I’ll let you off this time, so just leave—”

“Oh… I see…”

“—Huh? T-That voice… Abel?”

They hadn’t even noticed me.

And for some reason, that fact gave me a strange sense of relief.

Why…?

“What…? That guy… he’s your fiancé, Millia?”

“Wait, no… Abel, this isn’t what it looks like!”

A clumsy, far-too-late excuse.

Without listening to her, I spoke.

“So I was living… for something like this?”

＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿

Hello to new readers, and welcome back to those who read Gamer Assassin.

I’m Sora Akatsuki, and I’m excited to announce the release of my new work.

This is my first time writing an isekai fantasy, but I hope it aligns with your tastes.

I’m building up a stockpile of chapters, but I decided to release this to keep my motivation going. Updates will be slow like a turtle’s pace until I reach my goal, but once I’ve written more, I might post regularly again.