Haruka's younger sister who initially looked up to both Takayuki and Mitsuki like older siblings. When she discovers they've been secretly dating, everything changes. While Haruka's in the hospital in a coma, she visits every single day—there's no one else around to keep her company, but honestly, that's beside the point. The visits show how deeply she cares.
She's a talented swimmer herself, though she's always felt overshadowed by Mitsuki's abilities. After the accident, her anger toward Mitsuki runs deep. Part of it stems from watching someone she idolized seemingly throw away her own talent and future. But it's also personal—Mitsuki slept with Takayuki behind Haruka's back, which feels like a betrayal on every level.
Over time, she works through it and moves forward. She eventually becomes one of Japan's top swimmers.
Content compiled by AnimeList.moe from publicly available sources.
