Muteki no Wing! Invincible Wing!

Synopsis

About a girl who likes taekwondo and saved, when she was little, a boy from a local mob. Now she's a high-schooler, and still loves the sport. One day, she gets bullied while handing out pamphlets. A boy appears and defeats the bullies. She's so happy she kisses him. It turns out to be the boy she saved when she was little. (Source: Mangaguide)