Kyūsuke goes to elementary school with Chibiusa and is known for being both athletic and sarcastic. He's pretty much her friend group's go-to guy for anything physical, though he's got his moments of jealousy and insecurity like anyone else.
The Amazoness Quartet target him in Episode 155, specifically JunJun. At the time, he's working through a fear of the vault—basically the only gymnastics event that trips him up during an athletic relay. JunJun tries to peek at his dream mirror by scaring him into jumping over it, which actually ends up helping him push past the fear. After Sailor Moon and Sailor Chibi Moon step in to save him, he finds the confidence to keep competing.
Later on, when Chibiusa befriends a boy named Hiroki who's obsessed with building a flying machine, Kyūsuke doesn't hide his jealousy at first. But he comes around pretty quickly. Instead of staying bitter, he becomes Hiroki's biggest cheerleader, encouraging him to keep going through all the failed prototypes. Kyūsuke tells him that dreams don't mean less just because you need someone else's help to achieve them. Turns out he was right—when Hiroki realizes he doesn't have the stamina to keep the machine airborne on his own, Kyūsuke pedals alongside him and the thing actually flies. It's kind of a turning point for both of them.
Content compiled by AnimeList.moe from publicly available sources.
