This work depicts a "five" locked room mystery drama about two high school students, which develops in the first train in the early morning, the family restaurant after school, and the gondola of the Ferris wheel. A word that suddenly changes from everyday life to extraordinary, a psychological warfare on searching each other's minds. Youth, a fragile blue human figure, is depicted in a peculiar situation called a locked room.—MyDramaList

Ep. 1: Sappukei (Anna Yamada) and Katogi (Daiken Okudaira) are high school classmates. They have yet to talk to each other. One early morning, they both catch the first train. Why did they catch the first train? They make conversation with each other.—AsianWiki