Responses
Nevermind... I found it.
It was this: http://www.mangago.me/read-manga/teppen/
Sounds interesting, I'll read that :D
Haha, please do (=・ω・=)
I read it a looong time ago, so my memory is a bit fuzzy.
But I think it was a non-yaoi (shoujo, gender-bender, perhaps?). There was a girl (I think), who came from another country (USA, probably) to Japan. I remember she looked like a guy and dressed like one too, so she was mistaken as a guy and ended up as an idol, I think, alongside some guy.
I definitely remember that, when the girl got upset/ lost her cool, she would start speaking in English.
Please, help!