One year after the events of the anime, Rintarou begins to feel the repercussions of extensive time travel, and eventually completely fades from reality. Kurisu, being the only companion to remember him, now must find a way to bring him back.

One hot summer day a little girl gets lost in an enchanted forest of the mountain god where spirits reside. A young boy appears before her, but she cannot touch him for fear of making him disappear. And so a wondrous adventure awaits…