"We really met, didn't we...?"

One day, shortly after entering high school, Makoto Natsume is approached by his classmate, Aki, a girl he's never met before.

Aki says that ever since she was young, her great-grandmother had shown her a drawing of fireworks and told her that "someday you will meet Makoto Natsume."

Makoto and Aki investigate the secret of the drawing, which Makoto has no memory of. Contained within it is a precious "promise" exchanged in the past...

[Source: Hakuhodo DY Music & Pictures]