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 about is her senior kunoichi Botan who she has longed for.

At that time, Botan is sneaking into the merchant's mansion. Together with two of "herselves" which she created by her signature art of ninja "Kagebunshin", she beats watchmen down. There comes, however, the merchant carrying Yasuzu who has totally been screwed up. Botan and two of herselves get caught by Demi-Ogres in an off-guard moment...

(Source: DLsite English)