Okay, the big question is, "Why Nasutei and Seiji?" Well, my question to you is, "Why not?" The biggest reason I see them together, is because they have the most proof, and the others just don't make sense.
ALL THE WHY-NOT'S:
The most rediculous pairing I've ever heard of (and I've heard some doozies) that people actually support, is Shuuten and Nasutei. ???????????? Come on people. You are REALLY stretching your imagination to pull that up. She spends an episode or two with him, says about five lines worth of stuff, and then they go their separate ways. Everyone seems to get a kick out of the fact that he gives her the Jewel of Life. What, you think he's going to give it to a seven year-old kid? I mean, Jun definately wasn't responsible enough to take care of such an important item. An adult was needed to make sure the Jewel of Life was taken care of.