The protagonist was weak but now he is really powerful however he still looks weak. it's a martial arts manga and I think the protagonist uses muay Thai to fight. the latest chapter I can remember from it was that the protagonist was fighting this American guy because he was making fun of japan. thanks in advance.

Sounds like Tiji-kun!.

no I think the main character decided to take muay thai because his love interest didn't like weak people so he wanted to become stronger

I don't remember an american in the whole Tiji-kun! manga, much less him insulting Japan.

You can browse these tags : Muay Thai and Kickboxing
Not much listed, so it shouldn't take you long.

Your description does remind me of Karate Shoukoushi Kohinata Minoru. It's about karate mainly, but the main learns from muay-thai too at some point for his kicks. It has the girlfriend looking up strong people, and the MC facing some american in a bar or something, where illegal fights happen.

Last edited by oneeyed at 7:58 pm, Sep 7 2014

Is it history's strongest disciple kenichi? That's the only karate one I know.

Is it Hakaiou Noritaka!?

Yeah this is it thanks