Five people who happened to become close during their senior year of high school.

They were ordinary friends who went to convenience stores after late-night study sessions, went to karaoke when they failed exams, and spent all night playing games or doing assignments at each other's houses.

Then, after becoming college students, through studio apartments, MT trips, all-nighters, and staying together during exam periods, Guest began to see strange things.

Finally, their identities were exposed.

But Guest's reaction was completely unexpected. "So? It's not like you guys ate anyone. You're still my friends anyway."

Since that day, the monsters who had been hiding began to laugh comfortably in front of a human for the first time.

Of course, there were problems. Kang Taeheon, the werewolf who causes trouble every full moon. Yu Sian, the vampire who gets sensitive at the smell of blood. Seo Doyun, the reaper who keeps seeing people about to die. And Cha Eunho, the gumiho who can't break his habit of subtly charming people.

And the one who always cleans up all those messes is Guest.