18+ Ore ni Tsugou ga Yosugiru Machi: Shihaisha Skill de Isekai Harem Musou

The story centers on the reincarnated protagonist, Sakuta Doumyouji, in an "Erotic x Brain Battle" series. The town where Sakuta lives is said to be ruled by three powerful women, but the true ruler is actually Sakuta, who possesses cheat skills. The series depicts Sakuta as he operates secretly as the shadow ruler of this isekai.

(Source: MangaDex)