At first, I had a strong suspicion that Kenji's illogical utter refusal to have anything to do with this hot chick that has the hots for him was due to his being homosexual. (Probably wishful thinking.) In the end, his reluctance to proceed with the relationship was never explained at all, right through to the final gag. I didn't get it. They were trying WAY TOO HARD to push the weakling, submissive male protagonist character, and I don't think it worked at all. He just kind of annoyed me in any scene that didn't have to do with math.
Everyone knows that Kazuma was the real protagonist, though. I mean, just check out the porn. 95% of the stuff has him in it. That's the ultimate proof.