My Girlfriend Was Cheating With My Senior

I, Yu Isshiki, felt my hands trembling when I saw it.

…No way… This has to be a lie…

But what appeared on the smartphone screen conveyed their relationship with cruel clarity.

(Kamokura-senpai): Karen, are you home yet?

(Karen): Yeah, just got in.

(Kamokura-senpai): I just got home too. But I already miss you.

(Karen): Me too! I can still feel you all over me…

(Kamokura-senpai): [Thumbs up sticker]

(Karen): [“You’re the best!” sticker]

(Kamokura-senpai): Karen, that was seriously amazing. Why don’t you just become mine exclusively?

(Karen): Eh~ but Senpai, you have a girlfriend. Sakurajima-senpai.

(Kamokura-senpai): I know, but I think our physical chemistry is seriously on another level.

(Karen): I think so too.

(Kamokura-senpai): Right? That’s why I want to do it more.

(Karen): We’re already doing it once a week as it is.

(Kamokura-senpai): I want to do it every day!

(Karen): (lol)

(Kamokura-senpai): Even you said it, Karen. That I feel way better than that Isshiki guy.
…

KamokuraI couldn’t bring myself to read any further.

Just the part I had scrolled through was enough.

I took a photo of the screen with my own phone.

There were several similar exchanges.

The dates were, without a doubt, days when she wasn’t with me—days Karen claimed she was “meeting friends,” “going to dinner with family,” or “working on a report for tomorrow.”

But on those days, Karen Mitsumoto—the girl who was supposed to be my girlfriend—was actually meeting Tetsuya Kamokura, a senior in my club.

…At love hotels, and various other places.

If you look at online relationship advice for women, they’d say the boyfriend is the one at fault in times like this.

—It’s the boyfriend’s fault for not trusting her.—

—She cheated because the boyfriend didn’t treasure her. He got what he deserved.—

—Checking someone else’s phone without permission is unacceptable. You’re the worst!—

I slipped Karen’s phone back into the pocket of the jacket she had been wearing.
Karen had recently switched phones.

Apparently, the fingerprint sensor was finicky, so she had switched to using a PIN.
I knew that PIN.

It was her ex-boyfriend’s birthday.

I had found out that date by chance.

So, when Karen’s phone vibrated and the caller ID showed “Yoko-senpai,” I opened the screen.

I did it because “Yoko-senpai” is a senior at my part-time job.

She and Karen shouldn’t have known each other.

And when I opened it, the content I just described was what was displayed.
We were at a love hotel.

Karen was currently in the shower.

I threw on my discarded clothes and left the hotel.

On the way out, I sent her a message:

“Something came up. I’m going home.”

I didn’t head for the station nearest the hotel; instead, I wandered aimlessly.

If I had stayed there and looked at Karen’s face, I don’t know what I would have done.

Would I have interrogated her violently? Would I have broken down crying? Or would I have raised a hand against her?

To avoid all that, I left the hotel alone.

I was in such a state of shock that I couldn’t think straight.

My head was spinning.

It felt like I was in a daze, or some kind of dream.

…That’s right, if only this were all just a bad dream…

But I knew this wasn’t a dream.

It was reality.

I—Yu Isshiki, a first-year in the Department of Information Engineering, Faculty of Science and Engineering at Joto University—

Was being cheated on by my girlfriend—Karen Mitsumoto, a first-year in the Department of English and American Literature, Faculty of Letters at Joto University.

The other man was Tetsuya Kamokura, my senior from high school, university, and our club.

My heart felt like it was tearing apart, yet at the same time, it felt completely hollow. It was an indescribable feeling.

Before I knew it, I had walked as far as the banks of the Edogawa River.

The cold night wind blowing across the water whipped against my face.

But for my feverish head, it was just right.

I sat down on the bank and stared at the river for a long while.

…That bastard Kamokura. Why did he have to lay a hand on Karen? Even though he has such a beautiful girlfriend of his own…

Tetsuya Kamokura’s girlfriend, Toko Sakurajima, is a second-year in the same department as me at Joto University.

Yu Isshiki, Tetsuya Kamokura, and Toko Sakurajima—all three of us came from the same high school and were in the same department at the same university.

Toko-senpai had been a famous beauty since high school.

She was the president of the Literature Club and a library committee member.
Because she was always in the library, she was often called the “Goddess of the Library.”

Even after entering university, she was nominated for “Miss Joto University,” but she turned it down herself.

People said that if she entered, her victory would be guaranteed.

Toko-senpai isn’t just beautiful; she is graceful.

At the same time, she is a dignified and talented woman.

She isn’t stubbornly prideful, but she is an intellectual beauty with a strong sense of self.

Since high school, I—like everyone else—had admired Toko-senpai.

And that Toko-senpai had started dating Tetsuya Kamokura, who was a year above her, after starting her second year of university.

…Does Toko-senpai know that the Kamokura guy is cheating with Karen?

Suddenly, frustration and rage surged within my chest.

“I can’t let this slide.”

That thought took over my mind.

I pulled out my smartphone.

I selected “Toko Sakurajima” from my contacts and pressed the call button.

She picked up after about three rings.

“Yes?”

I said:

“Toko-senpai. Please cheat with me.”