Flexible Kid

Overview

Junior high student Mao Hoshimi is a small and somewhat effeminate but otherwise typical boy. At least he is until he turns into a girl while hitting the baths with his best friend Shunsuke Hidaka! But this is the least of his shocks--Mao learns he is actually of alien descent! Because the numbers of his species are so few, Mao learns, its members have the ability to change shape to breed with other species--and also to transform from male to female and from female to male to suit a potential mate. It seems that, now that Mao is in puberty, he is fated to become a suitable partner for whomsoever he comes in close contact with, be it Tomoko Yokawa, the cute girl he just met, or, to his horror, Shunsuke!

Source: AniList