One day, my best friend suddenly turned into a sickly girl from the TS

“Hey, hey.”

“What is it?”

“TS disease is amazing, isn’t it?”

“You’re right.”

Walking home from school, I nodded in agreement with my best friend’s words.

Walking beside me was Asahina Yoru, who made my ordinariness pale. His dyed brown hair was stylish, and our high school’s lax rules allowed it.

He was popular among the girls, and I often got asked to pass letters to him… But he never dated anyone.

“I can’t play with you when I’m dating my girlfriend.”

“No, no, it’s better to have a girlfriend than a male friend, right?”

“Really?”

We had this conversation once, and honestly, it made me happy. Having a romantic relationship is a milestone in a high school boy’s life. But to be told that our friendship was more important was truly heartwarming.

I’ve known Yoru since middle school, and he’s a genuinely good guy. I cherish him as my best friend and have decided to always be there for him.

“So, what’s the story about the TS disease?”

“Yeah, that’s right. Going from man to woman out of nowhere is bad. Everything up until now will change, you know?”

I nodded.

Today, one of the strange diseases is called TS. It’s one of the diseases that only men develop, and it’s a terrifying disease where once they grow, their gender turns into a woman.

“It’s like something out of a manga.”

“Yeah. Well, I guess it’s not that unusual now.”

It has been confirmed not only in Japan but in the world as well.

The cause is unknown, and there’s no cure, forcing those affected to abandon their lives as males and live as females. Though rare, the disease doesn’t pose a life threat, so it’s often shrugged off as something to deal with if it happens.

“What if I become a woman?”

“Stop it. I don’t want to think about it.”

“You’re right!”

We laughed together and then parted ways.

I always thought our relationship would never change, but fate can be cruel… I never imagined what would happen next.

It was just an ordinary day.

I had planned to hang out with Yoru the next day, but he abruptly canceled in the morning.

“Did something happen?”

I wondered if he had a secret date with a girlfriend. It wouldn’t be surprising, given how handsome he is. Disappointed, I decided to stay home and play games.

The weekend passed, and Yoru didn’t show up at school. The teachers said nothing, and he didn’t respond to my messages.

“What’s up with him? Sick?”

“…Maybe.”

Everyone was worried about Yoru, but like me, they had no idea what was happening.

Worried he might be seriously ill, I decided to visit his house after school. His mother seemed reluctant to let me see him, which was odd.

“…But, well, it’s about time he moves forward.”

“Ma’am?”

“Yoru’s in his room now. Yuki, can you see him?”

“Uh, sure…”

What’s going on?

With a strange sense of foreboding, I headed to Yoru’s familiar room. A gloomy air emanated from behind the door, making me hesitate.

I knocked lightly.

“…Mom?”

“…? No, it’s me.”

“Yuki?! Why are you here… Stop, don’t open it!!”

I wasn’t in the wrong room, was I?

The voice from inside was unmistakably that of a girl… Realizing this, I spoke again without opening the door.

“Yoru… I have a hunch.”

Honestly, I was more surprised than anything else.

I could tell from the voice that panic was setting in, and most importantly, I understood that Yoru was suffering. So, all I could do was try to calm him down.

“We’re best friends. That’ll never change… No matter what I see of you, that won’t change. I’ll leave because something has changed. Don’t be stupid. How many years do you think I’ve been your best friend?”

“…But I… I…”

His voice grew thinner, seemingly reflecting Yoru’s feelings.

“Yoru, if you’re ready, open the door. But if you’re still not ready to face it, I’ll leave for today.”

“……”

…I’m still not certain if it’s that disease, but I’m almost sure it is.

I’m truly shocked, and I can hardly believe it. But if it’s as I suspect, Yoru must be suffering. That’s why I said what I did.

…I waited a while, but Yoru didn’t open the door.

Alright… I should leave today.

“Yoru, I’m going to leave now. I’ll come by again tomorrow… Maybe we can play games or something…”

Just as I said, the door slowly opened.

There stood a beautiful girl clad in familiar pajamas.

“… Yuki.”

Her shoulder-length brown hair was disheveled, her eyes red and teary, and the dark circles under them were severe. She seemed slightly shorter than usual, and the buttons of her pajama top were struggling to contain her newfound curves.

“…Yoru?”

“…What should I do, Yuki?”

She slowly approached me and then pressed her forehead against my chest.

“…I’ve… become a woman.”

This was the change in my life – in Uozumi Yuki’s life.

The beginning of my days with my best friend, who had contracted the TS disease, recognized as a rare illness.

【A|N】

That’s why I got involved with a T.S. yandere that I didn’t know was in demand. I don’t know what will happen, but I’ll count on you all for this work again. It’ll be an experimental story, so I’ll write it down quickly.