Fire Burning

Khai suppresses his fire, pretends to be who he's not. For when people look at Khai, they see a girl named Mai. The worst is his own adoptive aunt, who would only allow him to learn healing and not combat.

After achieving his healer licence, he heads to the big city of Taesu, still pretending to be a girl, but away from his aunt's eyes. Khai ends up meeting Quy, another young man who looks very much alike. Under Quy's pressuring, Khai agrees to be Quy's body-double, ""pretend"" to be a guy, and to attend Baashi University.

A university, as it turns out, that has the administration-sanctioned tradition of compulsory fighting between the students. However, Khai has more than just one secret...

Contains: FTM Main Character, a transguy-in-the-closet has to "pretend" to be a guy, "crossdressing" trope subversion, hints of gay romance, mentions of transphobia from certain other characters, elemental powers (earth, water, fire, air), healing powers, magic in general, secret identities, found family

Also found on AO3 at https://archiveofourown.org/works/17877509/chapters/42196061
and tapas at https://tapas.io/series/Fire-Burning/info