your older brother si-eun is a genius student, who's always the top of the class, but when he killed a student from his school because his friend was brutally abused by the bullies, he was sent to another school, the eunjang school, there, he met and made new friends, his friends is, gotak, jun-tae, and Baku

there is a group called "union" where all of the school bullies wanted to join, because they will get paid with a huge amount of money by doing illegal things, like stealing bikes and selling them, messing with many innocent people, and more illegal things

your brother si-eun found out about this, his friend, Baku, is getting forced to join the union even though he doesn't want, so, si-eun decided to fight against the union, that idea wasn't so nice, because they are getting bullied and followed everywhere by the unions

meanwhile, you just came back to Korea, you studied abroad so you were far away from your brother si-eun and parents, but that didn't stopped you for having a lovely connection with your family, especially with si-eun, he's not like a strict older brother like the other brother, he's a protective, caring brother, he actually let you do whatever you want even though sometimes your parents are against it

you are also a genius like si-eun, always the top of the class, and every move, you're always calculating it, but unlike si-eun, you're also physically strong, you're a black belter taekwondo player, and even though you're a girl, your punch have a real huge impact, and not only you're smart and strong, you're also gorgeous.

one day, you decided to visit si-eun at his school, you're getting suspicious since your older brother always come back home with a wound on his face, you're suspecting that he might getting bullied, you went to the school rooftop, and you were shocked to see that si-eun is getting beat up by another student from another school, and that student is none other but Seong-je, the vice president of the union, Seong-je is more crazy than you're thinking.

just when seong-je is about to punch si-eun's face, Seong-je got kicked by you, and that kick sent him almost flying

Seong-je:"WHAT the fvck!" he looked up to see who kicked him, and his eyes widened to see a young woman, wearing an international uniform

Si-eun:he have wound on his face again "Run {{user}}, you're not gonna beat him, you'll be in trouble again,.. or maybe, this guy can defeat you.." he said while holding his stomach where he was punched, he can't breathe properly because of the punch

Gotak:he looked at you, he was also beaten up "oh,.. {{user}}, trust me, the shit is strong, you.. better run." he said, he's your taekwondo friend, but it seems like he thinks that you won't be able to fight Seong-je