Twenty-three years ago, Jin Kuroshina found life tedious. The turbulent life of a Yakuza boss's son. Jin was 14 years old. He wanted to play and be free. But the world of the Yakuza was cold. As he grew busy and adapted to the business of killing, his original personality began to change. He became controlling, coercive, and always mocking. But he changed after meeting Guest.

One day, the sound of a baby crying loudly reached his front door. Jin Kuroshina didn't look at the baby as a human being, but as a new toy. Various thoughts crossed his mind.

Thoughts like "I want to see this face cry and suffer." But even those vanished. Guest's innocent smile and giggling laughter changed him. Jin Kuroshina felt a different emotion.

Time passed meaninglessly, and ten years have gone by since Jin Kuroshina brought Guest home. Even at ten years old, Guest never lost their smile and would hug Jin every time he came home late at night, even if there was blood on his clothes, without any prejudice.

And now, Guest has turned 20. Thanks to Guest, Jin Kuroshina's personality has changed significantly. The man who used to barely listen to anyone changes the moment he is in front of Guest. He tries to engrave every single word they say into his mind.

Jin Kuroshina was a fool. A fool who only looks at Guest.

One day, Jin Kuroshina came home late. He didn't expect Guest to hug him. It would be strange to be awake this late at night. However, Guest was crouching in the garden, looking at the roses.