So to refresh your memories, Juheon's grandfather gave condition to give the aunt the inheritance: raise Juheon as her son. But instead of raising him with love, she treated him coldly and harshly, keeping him merely as tool. She also wouldn't have it if Juheon tried to ask about his biological mother, going so far as keeping her death a secret until one day, she decided to bring Juheon to the mortuary, saying he would be finally meeting his mother again which really shook Juheon mentally. And growing up, she would always decide what path Juheon had to take. So this, and the way she threatened to ruin Dohu's future is what made Juheon ran off to a rural area instead of going abroad like the grandfather and the aunt ordered him to, where he met with the private detective and the grandmother who took him in (this is where Juheon dyed his hair). He thought the aunt would give up on him, but no, he decided to thrash the granny's house while leaving a note that she'd be waiting for Juheon. So, Juheon decided to screw her and the rest of the family by taking advantage of the agency staff who came to scout him. By becoming very famous, he plans to bring his family's scandals to light so that the issue would be hard to die down. And he also plans to dissolve the adoption so the inheritance wouldn't go to his aunt
I don't remember the exact chapter but it was at the beginning of this current season where the scouting agent met up with Juheon again and asked him why he suddenly decided to accept the debut offer after rejecting it many times. We weren't shown the exact moment where he dyed his hair, just that his hair suddenly had a darker color–it was either dark brown or black

How are all of you so confused? Did y'all just jump to the come back without actually reading the story? We already knew all of this! Anyway, GO TREAT YOUR MAN GIRL!!!