Onsoku Hishō Sonic Mercedes: Futago Heroine Chōkyō Shirei!

Onsoku Hishō Sonic Mercedes: Futago Heroine Chōkyō Shirei! (which roughly translates to Speed-of-Sound Flight Sonic Mercedes: Twin Heroine Training Instructions!) is a hentai visual novel with simulation elements which puts the player in control of a villain who defiles magical girls. At the start of each day, the player can choose which sexual acts to perform on their prisoner to defile them. These scenes take place between visual novel-esque segments which advance the story. The game has multiple endings that can be achieved depending on the player's decisions and features voice acting for all significant characters except the protagonist.

An evil organization known as the Ars Magna rampages across Japan in search of the Elemental Cores, magical artifacts which imbue their owners with immense power. Their campaign is opposed by two magical girls, the twin sisters Sonic Mercedes and Sonic Gisele, who derive their power from the Elemental Cores stored inside their bodies. One day, the Ars Magna leadership commands one of their members named Max and his partner Tesla to challenge the magical girls with a homunculus named Mattel, who has an Elemental Core of his own. In the subsequent battle, Mattel overwhelms the magical girls, allowing Max to take one as his prisoner. However, when Max tries to extract her core, he finds that it cannot be removed from a pure soul. Max instantly realizes what needs to be done: his prisoner's soul must be defiled.