Emerged

In this world, there's a phenomenon which closely resembles what happens to clownfish called 'Emergence'. The purpose was to maintain a fixed ratio of men to women. When there are few women, some men changed into women. There are about hundreds of the same cases in Japan every year. The emergence usually happen to young boys. If happened to teen and older, the emergence process will be a burden which the body could not withstand. Thus, the mortality rate in these cases are low.

Tsukishima Kei, who has been living his life as boy for 18 years, emerged as a woman on the day of his high school graduation. For sure, she was confused, insecure and anxious. Especially when she was about to step to the college world. With a twist of fate, a senior of hers came to help her after years since they last met, who happens to be her first love since when she was still a boy and got rejected. Oh how awkward this will be.

~
Girl!Tsukishima Kei x Kuroo Tetsuro. CollegeAu.
The world they're in is based on the manga 'Kanojo ni Naru Hi' by Akane Ogura. The idea of the world all credit to Akane Ogura.
DIsclaimers: I don't own the emergence phenomenon idea. This may works as a spin off from that world. Also, I don't own the cover.