This is a love letter to the specific moment before ambition gets complicated, when two kids promise to go to space and actually mean it. The planetarium setting isn't just window dressing; it's the story itself, that exact space where wonder lives before doubt moves in. If you've watched Space Brothers, you already know why this matters: it shows you the dream before the cost, and that's something the main series can never give you back.

Set during a single summer of Mutta and Hibito's childhood, this short film tells an original story from the Uchuu Kyoudai manga by Chuuya Koyama. It is the summer when the two brothers promise each other that they will go to space. That same season they meet a young girl who also carries a wish of her own. The film mixes comedy, science fiction and everyday slice-of-life moments. It first played in Konica Minolta planetariums around Japan and was later released on DVD with the limited edition of the manga's twentieth volume.