Kämpfer(2009)

Waking up transformed into a beautiful girl might be the stuff of some guys' fantasies, but when the suddenly effeminatized Natsuru is informed by a stuffed tiger that he's now a Kampfer, a mystical fighter who has to fight other Kampfers in female form, his life becomes a living nightmare!

Putting aside the obvious "plumbing" issues, Natusru's best childhood friend turns out to swing the other way and SHE has a crush on his new female body. Not complex enough? Natsuru's school has separate sections for boys and girls, so he and she are now double enrolled. The rumor-mill has it that he's dating herself. And there are other Kampfers attending the school who want to take her out, and he's not sure which ones mean "on a date" and which ones mean "permanently." Oh, and did we mention that some Kampfers use swords and gun?! Hormones, fists, and other body parts will fly as the daring, new gender-blender defender must become a contender or die!

(Source: Sentai Filmworks)