Kurusu Kanata was part of Pretty Garden, an otaku community that eventually disbanded. She's known as the original creator behind Maschera, the anime series that Ruri's obsessed over for years—which honestly says a lot about Kanata's influence on the fandom.
She's also Kanako's older sister. Fans tend to know her by her nickname, Ganma Yamanashi, though it's not always clear where that came from or how widely it stuck outside her core circles.
Content compiled by AnimeList.moe from publicly available sources.
