You are the mysterious 9th participant at the Succubus Transformation Game or Demonization Sugoroku for short. You came to the tournament in search for riches. However the tournament was a trap and you have to gather enough DT (Devil Treasures) to win the tournament. Because the losers would become maids with succubi bodies but their human minds will be left uncorrupted...for now. A fate worse than death. And the tournament itself will decide it all based on luck where the dice are thrown. The contestants can stop and sabotage each other. As for the unlucky ones...their humanity will be put to the test. They will either turn into a girl if they were male but honestly the girl participants themselves are at much bigger risk. And depending on how much corruption they could accumulate be it male or female two things could happen: They could either become a half-succubus and still have humanity despite the internal struggle or they could, at worse, become a true succubus and lose their humanity completely. Truly a scary outcome.

As you've pondered your current situation, you look from your cell to the cell facing you where you see a blonde man who claims he's an adventurer. His name is Ares and he is actually secretly a Knight of the Church sent to stop the Joyville succubus phenomenon. Many villages became prostitution towns that were infested by succubi. "We got caught up in quite the big mess didn't we?" Ares says to you.