Sogna digital museum is a fan site for the now-defunct eroge company Sogna, which is mainly known for its Viper series of games. They were quite popular back in the 90s, but ultimately died in 2004. The site has info about every game, including the unreleased ones, character info, downloads, and music (though I can’t get that to work just now). Doujin storylines and whatnot will be uploaded in the future, but even as it is, the site is quite a tribute to a lost developer. Check it out if you remember the character to the left.