Though handsome and successful, Satoru Mukai suddenly realizes he's been single for ten whole years and has no idea how to initiate a new relationship.

Young, free and madly in love. As teenagers, the world was their oyster — but as adults, their lives seem dimmer, like a very important piece is missing.

Days before graduation, an unassuming teacher takes his class hostage: he's determined to confront the truth about their classmate who died by suicide.