Natsu-iro no Sunadokei
English name: Sandglass of Summer Colors
Genres: Drama, Romance, Sci-Fi
Type: OVA, Episodes: 2
Aired: May 21, 2004 to Jul 23, 2004
Studio: Picture Magic, Rikuentai
Source: Visual novel
Rating: PG-13 - Teens 13 or older
Synopsis:
Makimura Koutarou has made up his mind: during the summer vacation, he is going to confess his love to the seemingly unapproachable Serizawa Kaho. Yet, on the night before, he has a run-in with a strange girl - an encounter which propels him into the future. There, he learns that not only has Kaho-chan become his girlfriend, but she has also died in a tragic accident. Returning to his own time, Koutarou sets out to change the future and save his love.

(Source: ANN)