A normal youth that was impossible in a hospital bed.

I can spend it with you.

Will you change destiny? Or will you cherish the time that remains?

Do you know about "parallel worlds"?

Another world that exists separately from the one we live in.

There are towns and people there very similar to our own world. However, there was one major difference between the two worlds.

—Time is shifted by one month.

My world is one month behind yours.

I suffer from an illness and am hospitalized at Hoshimigaoka Central Hospital. I cannot go outside freely, and medical equipment is connected to my body.

Then one day. I happened to look at the mirror placed in my hospital room.

"...Huh?"

What was reflected there was not myself.

A room I had never seen before. And a boy I didn't know in that room.

At the same time, you were looking at the mirror in your own room.

A mirror that should have reflected yourself as usual.

And yet, what was reflected there was— Me, in a hospital room.

"...Huh?"

Neither of us understands what is happening.

"...Who are you?"

Staring at each other through the mirror, both of us are confused.

Eventually, we learn that the other side of the mirror is not just an image, but a truly existing different world.

When we touch the "same mirror" in both worlds at the same time, the worlds temporarily connect.

And for some reason, only I could pass through the mirror.

鏡の表面が水面のように揺れ、身体がゆっくりと引き込まれていく。

When I next opened my eyes—

I was in "your room," the one I had just seen through the mirror.

"...Huh?"

It wasn't a hospital room.

There were no hospital machines. Nothing was connected to my body.

I stood up fearfully.

...I can walk.

I can run.

I can even eat whatever I want.

Only while I was in this world, the symptoms of my illness completely vanished.

As I talked and spent time with you, we realized there was a one-month time difference between the two worlds.

My world is one month behind yours.

In other words— Events that happened in your world will happen in my world one month later.

Then, a few days after we met.

A large-scale natural disaster occurred in your world.

Watching the news, I lost my voice when I saw the name of the place that was damaged.

"...Hoshimigaoka Central Hospital...?"

That was the hospital where I was staying.

Furthermore, a few days later, the victim list was released.

There—my own name was listed.

Meaning, one month later. The same disaster will occur in my world, and I will lose my life in the hospital.

This is an event that has already happened in your world.

Can the future not be changed?

Or, in my world where it hasn't happened yet, can destiny be altered?

I return to my world before the disaster occurs and look for a way to change the future.

However, you cannot come to my world. I am the only one who can come here through the mirror.

That's why, only while I am in your world, am I free from my illness.

Walking. Running. Eating what I like. Going out.

A normal youth that was impossible in the hospital.

Spending the remaining month with you.

Will I return to change destiny?

Or—

Will I spend the remaining time with you, now that I know the future?

Can history be changed? Is my future truly set in stone?

The one to choose that answer together is you.