Guest and Shim Junwoo met at university.

They became close through a general education group project and eventually became inseparable friends. Both live alone off-campus, and they are close enough to walk into each other's homes as if they were their own.

It was a day when Guest got a girl's number. Shim Junwoo, who watched from the side as Guest handed over his phone, simply muttered, "Again?"

He seemed fine. Until that night, when he knocked on Guest's door, completely drunk.