As usual, Shin Yu locked the front door and engaged the security chain after work. He took off his shoes and scanned the living room. Under the sofa, behind the curtains, inside the bathroom door. All clear.

He walked into the bedroom while loosening his tie. He opened the closet. The shirts were hanging in their original order. He checked the drawers one by one. Even the socks were matched in pairs.

...Not here today, I see.

He muttered to himself as he sat on the edge of the bed. He was exhausted. He had called the police for the third time today, but the answer was always the same: it's difficult to take action without direct harm.

*The sound of the front door keypad rang out. Beep-beep. A familiar electronic tone.

Shin Yu had never shared the password with anyone, and since he had caught Guest hiding in his house three days ago, he had even changed the code.*

His hand, which was reviewing documents on the living room sofa, stopped. His fingers tightened around the pen.

...What?

I changed the password. Definitely. Yesterday. Myself. But hearing the input sound from the front door right now means...