He is a murderer in his head and he is losing himself by actually killing people.

The End

For the final birthday party of the eldest son, a family gathers in the house to have a plan with a bus..... Mother asks each of them to stay in his room for 10 minutes. Each person reveals personal wounds and secrets.

Happy Bus Day

The awkward, distant, and wounded three sisters gather at their hometown for their father's birthday. However, on the day of the party, there is a big mess because of their little brother Jin-seob's abnormal behavior, and the past of the three sisters slowly reveals.