For the Touhosu! feature request, see: Touhosu! / Dodge the Beat
Touhosu! is a feature request from 2011 which proposed a new game mode that combines elements of osu!catch and the Touhou Project (a bullet hell shoot 'em up video game series). The mode was inspired by the aforementioned Touhou Project, as well as an older feature request called "Dodge the Beat" that aimed to create a game mode in which players dodge fruits, as opposed to catching them like in osu!catch.
The feature request garnered significant attention from users, with over 522 total replies and 11,000 votes. However, as for now, there are reportedly no plans of adding Touhosu! or Dodge the Beat into osu!.