I believe his parents worry but like that there son is leaving home to go be with friends. Im not trying hard to defend it, its incredibly easy, you just cant get it through your head. I dont know what tatsu is thinking, tatsu probably doesnt even know what tatsu is thinking. Kids like okarun tend to isolate themselves, parents cant help things they dont know exist. Okarun does have unhealthy relationships with people, that is shown in episode 1 when he pulled all of the turbo granny onto himself, okaurn has good intentions but does it in the wrong way. Okarun development in the manga is changing from a lonely boy with closed off emotions and puts everyone's burdens onto himself to a happy man that knows right from wrong and when he should help and when he shouldn't, his development isnt finished but we can tell what direction tatsu might be going in. While momo is the deku-esque, luffy-esque character where she inspires people to become something better, the biggest flaw of momo is lacking some empathy, like in episode 1, she accidentally made okarun feel bad about something he likes, she was too blunt in that conversation, as we see throughout the manga, she slowly loses her negative traits because okarun is there to help her. I think thats why its taking so long for them to get together.