I get why everyone is trashing Rio because he is acting like a bratty kid but I don't see it like that. I feel bad for him, obvi he has felt this way for a while, that he is no one's #1. He sees his stepdad as someone who is taking his dad away from him, that's scary for a kid. I know he's 18 and blah blah but our thoughts and emotions become more intense/uncontrollable as we go through puberty. I just think he is alone in a world of people that 'love' him. Rio just wants one person that loves him and actually cares to get to know him.
Also the whole, he doesn't want to hug his dad because he old is bs. If a family member is gone for long periods of time i.e. 3 weeks usually you'd hug them when they get home. Rio's reaction is not one of a bruting teenager but of someone who is hurt.
I think Rio is fearful of losing Ritsu to another person, hence why he is so clingy and "shielding". I hope they stay together because I love them but I have a feeling this problem will continue to come up throughout this manga.
I swear if Dan goes back to jaekyung the second he apologizes I'm gonna be mad. Dan did not go through all that just for him to jump right back in. I hope he loses every match until he takes accountability for all the crappy things he did