Yu is a boy and twin to Ai, making him Rin's younger brother. He and Ai are basically a two-person chaos squad—constantly pulling pranks and getting under Rin's skin, though she clearly cares about them despite the headaches.
In one memorable outing, Yu and Ai are up to their usual antics, messing with Rin and swiping Nozomi's cookies. Rin snaps at them to knock it off, but seeing them upset, she softens and gives them a ball to play with instead. They team up with Nozomi and Urara to play, then spot Coco and Nuts and invite them along. Things get weird when Nuts suddenly talks, which catches Yu off guard, though Urara quickly redirects everyone's attention back to the game by kicking the ball.
During play, Yu kicks the ball directly into Gamao's hands. When Nozomi and Urara come to ask for it back, Gamao decides he'd rather destroy it. Yu and Ai beg him to give it back, but Gamao just throws it at them instead, scaring the kids. Rin steps in to protect them, taking the hit herself. Seeing their sister hurt, Yu and Ai rush to comfort her. After Gamao's defeated, things return to normal—just Yu, Ai, and Rin hanging out like usual.
Content compiled by AnimeList.moe from publicly available sources.
