ritsu needs to work on his communication FOR SURE he always wants to be seen as this reliable older figure to tsukasa... not realizing that he can also rely on tsukasa!! ritsu also has the tendencies to bottle up his feelings until they eventually burst, and he ALWAYS blames himself when something goes wrong. definitely needs to get his feelings sorted out first (if we're talking about canon he needs to move on from that bum mao isara ASAP)
for tsukasa i think its pretty obvious but he's a tad bit too perfectionist. not everything can be perfect and fit your expectations. i imagine that can be an obstacle when rtks have kids (you cannot tell me tsukasa doesn't have extremely high expectations of his children,,, he grew up in a traditional family after all)
i also somehow noticed that they haven't opened up to each other about their past/childhood at all??? i mean this is enstars we're talking about so i dont think it will happen like, ever, but it'd be nice if they can learn more about each other's backgrounds

tldr: ritsukasa need to open up to each other more, ritsu needs to get his feelings sorted out and tsukasa needs to change his mindset