Mitsuki has carried a secret crush on Takayuki for years, though she's friends with both him and Haruka. Back in high school, she was a serious competitive swimmer, but that all changed after Haruka's accident—she quietly stepped away from the sport to be there for Takayuki instead. When he sank into depression, she threw herself at him, eventually confessing her feelings.
The thing about Mitsuki is that she means well, but she bottles everything up until it comes crashing down in messy, sometimes harmful ways. She's also haunted by guilt over Haruka's accident, convinced it's her fault since she was the reason Takayuki ran late for his date that day. That weight never really leaves her.
Content compiled by AnimeList.moe from publicly available sources.