My Girlfriend Wanted an Open Relationship, So I Broke Up with Her and Found a Sweet Yandere

I felt myself stirring awake, my eyes still closed, my head heavy with sleep. I had rested well at Sensei’s place, yet somehow, here I was, drifting off again. There was something—no, someone—resting against my right shoulder, a light weight, steady and warm.

Reluctantly, I opened my eyes, only to be met by a streak of sunlight filtering through the train window. The rain had stopped, and bits of blue sky were poking through the clouds.

Slowly, I turned, taking in the pale skin, the blonde hair braided with meticulous care. Her long lashes fluttered slightly as she slept, her expression peaceful. Her face had this round, soft charm to it that could only be described as… cute. As for her personality, well, I was still working that out.

She wasn’t a stranger. Not quite a friend either. An acquaintance…? Classmate…? I couldn’t quite put a label on her.

“It’s rude to stare at a sleeping woman, you know, Takahashi-san.” Her voice, though soft, startled me awake. It was calmer than her usual tone at university, lower, more bearable somehow.

I flinched, recovering quickly. “Uh… Iroha-san, why are you here?”

She leaned away, giving me room to sit up fully. Her steady grey eyes fixed on mine as she answered, “Boarded the train. Walked in. Saw you. You were sleeping. So I slept too.”

“Oh… okay…” I replied, still processing her oddly clipped explanation. What’s with this way of talking?

This is Iroha Miyu. I met her about a month ago during the entrance ceremony… well, “met” might not be the right word. It was more like an accident.

Since then, she’s dropped the honor-student act around me—the perfect mask she keeps up for everyone else. We’re classmates and… that’s pretty much the extent of our relationship.

“Still, what were you doing here? Aren’t you supposed to be at university?” I asked, pulling out my smartphone to check the time. Only about ten minutes had passed since I boarded—one stop, to be exact. That meant she must’ve gotten on at the same station.

“I was going to your house to pick you up, but I was surprised to see you here,” Iroha-san said, her voice trailing off as she continued. “You spent the night at your girlfriend’s house, I guess.”

She knew about my relationship—I’d made it clear when we’d first started talking.

“Uh, nah. I didn’t…” I started, hesitating. I considered telling her I’d stayed at Sensei’s house but… yeah, no. That didn’t feel right, not at all.

“Oh…” she nodded, as if to herself, before her expression changed. “Looks like you broke up with her.” She kept nodding, entirely self-assured.

“H-how?” I stammered, caught completely off guard. Was it that obvious?

For a moment, silence hung between us as Iroha’s eyes widened. She pressed a hand to her mouth, clearly trying to suppress a reaction. A second later, she slid her hand down to her chest, her lips trembling.

“Don’t tell me I was correct?” she asked, her voice barely above a whisper.

…So she was guessing. A complete shot in the dark.

“…Yeah,” I admitted, a sigh slipping out as I leaned back into my seat.

After another beat of awkward silence, Iroha straightened herself and, with all the confidence in the world, declared, “I knew it. I always had the qualities of a detective.”

This damn girl. Instead of consoling me or saying something remotely thoughtful, she was just… well, her. Honestly, what was I even expecting?

Iroha Miyu. She may look like a prim and proper honor student on the outside, but inside, she’s missing a screw—an important one at that.

***

[At the Entrance Ceremony, a month ago.]

The sky was unusually clear that day. Not a single cloud in sight. The warm spring air carried the faint scent of cherry blossoms as I made my way to the university’s auditorium.

It felt strange—surreal, even—to be here. A new chapter of my life was starting, but it didn’t feel any different from high school. Maybe that was why I wasn’t particularly nervous. My hands rested casually in my pockets as I walked through the gates. A few students were chatting in small groups, their laughter echoing faintly in the background.

Inside the auditorium, it was another story. Rows upon rows of neatly dressed students filled the space, all waiting for the ceremony to begin. The atmosphere felt heavy, as if everyone was trying their best to appear dignified. I took a seat somewhere in the middle, not too far back but not in the spotlight either.

The ceremony itself? Long and formal. There were speeches from the dean, some professors, and even a student representative. They all spoke about seizing opportunities and the “privilege” of being part of this prestigious institution. I barely paid attention. My mind wandered to the crowd around me—the small gestures, whispers, and fidgeting hands. It was clear most of them were nervous.

When the ceremony finally ended, a collective sigh of relief swept through the room. I stood up, brushing imaginary dust off my trousers, and turned to leave. But as I approached the exit, a commotion caught my attention.

A crowd had formed near the entrance, the sound of murmured admiration and awe growing louder with every step I took.

“Who is it?” “It’s her, isn’t it?” “No way, she’s even prettier in person…”

I couldn’t help but feel curious. Crowds weren’t really my thing, but I stopped one of the students passing by.

“Hey, what’s going on?” I asked, gesturing toward the cluster of people.

The guy blinked at me, as if surprised I didn’t know. “You don’t know? It’s her! Iroha Miyu! The piano prodigy!”

I raised an eyebrow. “…Piano prodigy?”

“Yeah, she’s incredible!” he gushed. “She’s won international competitions, performed in Europe, and she’s barely our age. They say she’s going to be the face of the music department here. Isn’t that amazing?”

“Sure,” I replied flatly.

The guy gave me a look as if I’d just committed a cardinal sin but didn’t press further. He hurried off, likely eager to catch a glimpse of the so-called prodigy.

I glanced at the crowd one more time, my curiosity fading as quickly as it had come. It was none of my business. Another “genius” for people to admire. I turned around and walked away without a second thought.

That was the first time I had heard of her, Iroha Miyu…. I still regret not seeing her that time so I could ignore her later but well, some things are bound to happen one way or another.