Responses
No I thought he did TKD throughout high school and had a career plan to get into it until he broke his arm from that orange hair guy that was causing problems at the cafe and his parents found out so he had to quit.. cuz he told ML like a backstory about kids and taking care of them at the TKD studio place ╥﹏╥

It seems that he met the brother first. The brother was the one with the Taekwondo uniform in the last panel . I suspect so because Chaejun was too young and the uke couldn’t have been that old. Plus, the brother seems to think he looks familiar so it’s possible he has seen him before. I might be wrong though.