Maou no Musume-Tachi to Maguwaeba Tsuyoku Narerutte Hontou Desuka?魔王の娘たちとまぐわえば強くなれるって本当ですか?; Is It True that I can be Stronger if I Make Love to the Devil's Daughters?

Orphaned after the his parents were murdered, Uta Rain was ultimately auctioned off as a slave. Certain that he would be treated terribly no matter where he was taken, Uta was in despair. But what awaited him was... a luxurious meal and five pretty sisters. However, they were the daughters of the demon lord who was defeated by the hero 16 years ago?! Uta's fate begins to change drastically! (Source: Takeshobo, translated)