What is this story all about again? About finding Tay's brother or something?

No, its about guy who bring luck to his brother but always get fucked having little to no luck , despite all the difficulties he faced , he remained resilient and somehow charm one person who genuinely likes him and not because of his brother, the story is more about tae and illy how they both understand each other while finding his brother who is kidnapped and latter be brought back to unherdu , which will be cause of terrorism and other things