Natsu-iro no Sunadokei

With summer vacation about to begin, Koutarou Makimura plans to confess his love to the popular Kaho Serizawa. After a strange incident, however, he finds himself traveling through time, experiencing the vacation out of order. When he learns that Kaho is going to die just before they return to school, Koutarou must use his knowledge of future events to prevent her death, no matter the cost.