Viper GTS is a direct sequel to one of the stories included in Viper V-6, namely The Devil Came. In that story a frustrated man named Ogawa summoned the female demon Carrera and had to have sex with her until she was too tired to claim his soul. Now Carrera is back to hell, but the bored Ogawa summons her again. Only this time, she brings a partner: another sexy female demon named Mercedes. So now Ogawa has to satisfy their sexual needs. But the happy orgy is interrupted by the appearance of a new face - an angel from Heaven...

Like other Viper games, Viper GTS is very heavy on sexual content, to the point of being entirely pornographic. The sex scenes are animated. The gameplay is, per Viper tradition, reduced to occasional choice-making. Most of the times one of the choices is correct while the other leads to Game Over; however, there are a few parts where it is possible to slightly branch the story line (which in reality means viewing a different sex scene).