Based on the erotic doujin game by Enokippu (えのきっぷ).

One night in a merchant's mansion, a kunoichi (female ninja) named Yasuzu is violated by a group of men under the effect of "Aura of Ogre", called "Demi-Ogre". Although she had kept her virginity, the Demi-Ogres keeps sexually tormenting Yasuzu. Now the only thing Yasuzu can think abo...