Normally Niou would top my list, but after playing the Prince of Tennis "dating" game on my DS, I can't help but wonder if I actually got Yagyuu when I was supposed to get Niou and Niou when I was supposed to get Yagyuu. Because I swear those two switch on me!
So, unless it's Tenimyu Niou (ie Masa) I would have to go with Yukimura or Eiji. I don't think I can choose between the two of them. But Yuki and I are a great deal alike, so I don't know how long that would last. And he's still locked on the game, so I haven't played his story yet. I'm working on Chitose for the third time. Bastard keeps dumping me. *grumbles*