What is "mizuiro"

Mizuiro is a visual novel made by NekoNeko Soft released in 2001. It has versions for four different platforms: PC CD (3 Disc), Dreamcast, PlayStation 2, and PC DVD-Rom.

There were two anime OVA adaptations of the game, a two-episode hentai OVA in 2002, and Mizuiro 2003, a two-episode non-hentai OVA in 2003. Both have same characters, but with somewhat different storylines.