It is summertime, and Shinobu laments not having a boyfriend. She then happens upon a young man weak from hunger, and wearing a rabbit costume. She gives him a carrot, he expresses his gratitude by hitting on her... and she hits back. The young man leaves behind a key to another dimension where everybody's possible futures exist. Lum and Ataru join Shinobu to find the bunny boy, and happy futures for themselves.

The year is 1945. Everything as usual in the Fukuoka city. Some places in Japan have already been scorched by the fire of war, but here it is relatively peaceful and calm. The school still working, and the boys play war in their spare time. Daichi and his friend are the commanders of rival squads. One day a newcomer appears in the class - Yoriko, a girl evacuated from Tokyo. Yoriko takes life very seriously, she has good reasons - her childhood ended after the loss of loved ones in the bombing. Children get to know each other and become friends. They, as the rest of the city, do not yet know that on June 19 their life will be divided into "before" and "after".