Prolific eroge developer best remembered for the Viper series. Sogna Digital Museum is a site detailing the company and their games.
Animahjongg V3
Animahjongg X Perfect
Viper 10 RS
Viper 16 Rise/Imagine
Viper 6
Viper 8 RS
Viper BTR
Viper CTR
Viper GTS RS
Viper V12