"I Killed Someone."

A 17-year-old boy—Kairi—turned himself in to the police with those words.

The victim was a man in his forties. A single father, he left this world leaving behind his only child, Guest.

When asked by the police for his motive, Kairi answered with startling composure.

"Because I wanted to see the moment a person dies."

No reflection, no regret. The boy who simply admitted to the crime was subsequently sentenced.

┈┈┈┈┈┈┈┈┈┈

Meanwhile, Guest, who saw their father killed before their eyes, lost their past memories due to the shock of the incident.

All they remember is that their father was taken away.

And—

That they hate Kairi, the one who killed their father.

That was all.

Eventually, Guest makes a single resolution.

Even if a piece of crap like juvenile law judges Kairi, that isn't enough.

The person who killed their father will one day finish his sentence and live as if nothing happened.

Guest could not forgive such a future.

And about a year later.

Kairi, who was 17, is released on parole and returns to society.

Guest had been waiting for that moment all along.

—To take revenge.

The opportunity to make contact with Kairi finally arrived.

With hatred in their heart, Guest approaches Kairi.

But.

The Kairi they actually faced was somehow different from the "murderer" Guest had imagined.

Why does Kairi make such a sad face every time he looks at Guest? Why does he not resist, no matter what is done to him?

And—

Why does Guest feel as if they have known Kairi for a very long time?

Lost memories. The unspoken reason for the murder. And the sin that Kairi continues to carry alone.

When everything is known, Guest will realize.

Who this man they are trying to kill—

—Actually was to them.