I'm looking for manga where the protagonist or a main character has a weak appearance but is actually very strong.

It can be a realistic martial arts/sports manga or a very unrealistic supernatural fantasy manga.

Feed your head.

tiji-kun! came to mind.

Id 😀

[img]https://c1.staticflickr.com/1/753/22668593615_519ce54b81_o.png[/img]

Tenshi na Konamaiki aka Cheeky Angel. Title says it all. She looks girly and pretty and angelic and all that stuff but she can kick butt all the time. I prefer watching the anime though. It's a fun watch!

Trigun should fit i think hmmmm perhaps even Grenadier dunno abt tht tho

love Id
😃

perhaps even Ubel Blatt

This fits perfectly: Holyland - the guy used to be bullied a lot and looks like a very fragile kid but he trained really hard and now he has a very high fighting power (martial arts).

This one seems to fit nicely too: Deadman Wonderland, but he doesn't know he's strong and he's kind of a puss.

These sort of fit:
The Breaker
Junk - Record of the Last Hero - he's a hikikomori who used to be bullied but then he gets a sort of armor which gives him a lot of power.
Reborn!

The first two and Junk fit a little better than the others but I think that they all have some points where they fit your request.

Hope this helps.

naruto! ahaha 😀

the female protagonist of Yanki-kun to Megane-chan

I've already read everything everyone has suggested. I also do redraws for Holyland, so I'm more than up to date on it 😛

Feed your head.

Would Shijou Saikyou no Deshi Kenichi count?

Kenichi doesn't appear very weak anymore, but at the start of the manga he was the typical weak, bullied, unthreatening kid.

Eyeshield 21
Deadman Wonderland
Konjiki no Gash!!
Negima

[img]http://i1237.photobucket.com/albums/ff463/Asura007/Enishi-1.jpg[/img]

Rurouni Kenshin

He looks like a wimp. He's super short (all the other male characters tower over him) and thin, and he always acts/looks a little dopey. But in actuality, he's a super-strong ex-war assassin.