姫騎士リリア～魔触の王城に堕つ～

Princess Lilia is next in line for taking over her Kingdom, though her brother Prince Dirk wants things to go his way. He teams up with a demon in agreement that they will capture Lilia's "hidden power" which can only be gained by sending her into the highest level of sexual ecstacy. He captures both Lilia, her loyal Knights, along with his own mother, all for his own bidding. But can he get the "hidden power" in time for the demon?

[From MyAnimeList]