Neither, tbh.
It’s not as simple as Jaejoong needing Yunho more, because they need each other equally. Jaejoong needs Yunho for stability and guidance and dance lessons and smoothing over his rough first impressions. Yunho needs Jaejoong for help—a shoulder to lean on, a same aged friend to take on some of his duties as big brother to the group—and for singing lessons and for that flair of spontaneity that he just carries with him.
They reassure each other in their insecurities, they share the work load, they take care of the other members and spoil them rotten. Nobody is a bigger fan of Jaejoong than Yunho is, and nobody is a bigger fan of Yunho than Jaejoong is.
What we’re seeing now, with both of them suffering from depression off and on and just seeming a little bit…different…that’s not new. They’ve always been like that, but it was dealt with in private because they had each other to help through everything. Now they don’t. Sure, Jaejoong has Yoochun and Junsu and Yunho has Changmin, but it’s not the same. As close as they all are to each other, there are things that only Jaejoong and Yunho could do for each other just because of how close they are in age and how close they are as friends.
Yunho absolutely hides his emotions better. That quality is what landed him the leader role, and part of what makes him such a good one. Even if Yunho had a twitter and used it as often as Jaejoong does his, we would never get a tweet about his feelings concerning the whole situation because that’s not how he is. He goes drinking and “takes walks” and calls his friends and wallows, but he doesn’t put everything out in the public where it could potentially come back to bite him and the group’s image in the ass.
The main reason I think this separation will be good for YunJae is because they depended on each other too much. They got too used to being around each other constantly and being able to depend on the other to fill in their weak spots. Yunho and Jaejoong have always been together for as long as they’ve known each other. They were always in the same project groups in SME, always been paired up as YunJae the Couple, always been paired up as the leader members, hyungs to the three dongsaengs. They’ve never had an opportunity to learn how to depend on themselves for everything. Now they do.
Now they have no choice but to really start growing as people—real people, not idols or celebrities or members of popular groups.
