Uchuu Kyoudai: Itten no Hikari
Genres: Comedy, Sci-Fi, Slice of Life
Type: Movie, Episodes: 1
Aired: Jul 21, 2012
Studio: A-1 Pictures
Source: Original
Rating: PG-13 - Teens 13 or older
Synopsis:
The anime's original story features Mutta and Hibito during one summer when they were children. During the summer when Mutta and Hibito made their promise to go to space, they met a young girl who also had a wish.

(Source: ANN)