Teisou Gyakuten Sekai nara Moteru to Omotteitara

"A World Where Chastity is Reversed"—A dream world where the male-to-female ratio is 1:20, women have stronger sexual desires, and precious men live a smooth life protected by their bodyguards. Fifteen years have passed since Ikuto Ichise was reincarnated into this world, which should have meant having a guaranteed harem, but for some reason, he isn't popular. Ikuto laments that it must be because his bodyguards are all handsome men, and especially his childhood friend Rui Toosaka, who is particularly high-spec... but in reality, the bodyguards are beautiful girls disguised as men! Completely unaware, Ikuto is overly close and unguarded, making every girl feel like she has a chance. As he unintentionally forms an oblivious harem, Rui, who wishes to be seen as a girl, reveals everything to him—!? (Source: Kadokawa, translated)