![](https://cdn.animecharacters.io/images/characters/large/7249-d083d8f0.jpg)
Kyuutarou Hoshino (星野 九太郎)
Hachirota Hoshino's younger brother, he also displays a strong interest in space travel, and hence spends most of his time attempting to construct a working, miniature rocket, so as to prove his talent in that particular field. He maintains a shaky relationship with Hachirota, openly displaying disrespect for him. However he develops significantly throughout the series, especially after encountering Yuri Mihailokov.