Mugen = 19
Jin = 20
A 4 or 5 year diffrence isn't really that much of a big deal, in my opinion. At least she's not opting for
someone who's 30-40. Anywway, I'd say Mugen. To me, it surely hints that way, more so that, despite Mugen
saying he doesn't care, and being distant from her, HE is the one that always comes saves her, especially as he was
running off when Fuu was stuck in the brothel, but felt guilty, and went back. Where was Jin there? And he's not
even bound by duty like Jin is either, he could leave anytime. As for the Fuu asking Jin instead of Mugen to go with
Sara-san, I always thought that it was because she thought he would say no and stay, unlike Mugen, who would literally
jump at the chance and go.
Also, in a interview with the director, Watanabe, he specifically says, that Mugen (and Spike), are rebellious in
nature, and don't truthfully express themselves to the girls they actually do have feelings for. That would explain
Kohza and him ignoring her, acting like he didn't care for her, and yet when he was drowning, his last thoughts
included her (before her betrayal, of course), then Jin, and finally, Fuu as the final important person.
I would continue with the hints, yet, I feel that's enough for now. I just choose Mugen ^^.