See also: osu! (disambiguation)
The osu! game mode and osu! itself were originally based on rhythm games developed by iNiS for the Nintendo DS in the early 2000s. peppy built osu! to be a simulator and level editor for the iNiS games, and the earliest community members were generally fans of them too. Older beatmaps were heavily influenced by iNiS level design.
The games referred to are:
Box art for Elite Beat Agents
Elite Beat Agents is a western sequel to Osu! Tatakae! Ouendan! released in 2006. Some of its characters were present as osu! mascots in official artwork and skins.