Hello, I'm looking for a Shoujo manga who has the next details in it:
A Manwha/Manga:

- Main characted doesn't fall in love too quickly
- Main character is strong
- Main character is the jjang of the school, or boss of a gang * Jjang = The best, in this case the best fighter*

I kind of like these manwha's >:3 I've read much of these manga's already:

- Love in the Mask
- He's dedictated to Roses
- Boy of the female wolf
And much more.. But I can't remember all of them D:
So drop some manga's/manwha's here !! ★

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Twinkle twinkle little star,
How I wonder what you are..
Up above the sky so high..

i would recomend red lion it has everything you said its about a red haired girl that wants to quitbeing a delincuent and while she is harrased by 3 guys

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Gokusen- she's in charge of a yakuza group, though she's the teacher of the school.
Angel Densetsu, though it's all a misunderstanding, and you might be put off by the art.
Oresama Teacher is about an ex-delinquent gang leader girl, who... still fights a lot.

Possibly Penguin Brothers.

I don't remember if the main character fall in love quickly but i can suggest you Do You Want to Try?

Oresama Teacher
Red Lion

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Nulla in mundo pax sincera
"Always go too far, because that's where you'll find the truth." - Albert Camus

You can try looking through "slow romance", "stoic character" and "fighting" in categories.
But I second Gokusen.