The end of high school life.
The end of the "ordinary citizen" era.

Where did the car go—the one that hit Kobato-kun and vanished from a locked-room situation?
Depicting the largest incident in the series, the Winter volume marks the grand finale of the tetralogy!

Kobato, who aspires to be an ordinary citizen, is hit and run over one day and rushed to the hospital. When he wakes up, groggy, he is told that he has broken the bone in his right leg.

The next day, after undergoing surgery and being questioned by the police, a message is left at the bedside of the deeply sleeping Kobato from Osanai—who also aspires to be an ordinary citizen—stating, "I will not forgive the culprit." It seems Osanai is searching for the perpetrator... The Winter volume is finally published!