Ok I have vague memories about this manga, but basically, the uke has a twin brother. The seme (supposedly) has feelings for the brother, however, it may be due to a misunderstanding. The uke has an unrequited love for the seme, but he's quite insecure and self-conscious. In the end, they worked out their feelings and got together. It's pretty angsty but sweet towards the end.

Another detail worth mentioning is that the characters wear some kind of traditional clothes. They seem to be live in a tribe or sth.
That's all I can rememeber. May got some details wrong but if anyone has any idea, please drop a link! i'm desperate! Thank you!

It's not quite as you described it (there is no twin, the uke disguises himself as a woman), but the rest fits with:

[img]https://www.mangaupdates.com/image/i184385.png[/img]

Wild Rock by TAKASHIMA Kazusa