Another thing I really like about Ozaki is that he really doesn't do anything for profit, or 'personal benefit' like you said. Although through his skill he's managed to become one of the respected village heads and he's the ringleader in the Shiki extermination, it's not because he's always striving to get to the top like one would think. At least, that's not the vibe that I get from him. It's not about being a leader, it's about getting the job done.

I think it's interesting that despite conforming more to the system than Seishin, Ozaki is actually more quick to abandon his beliefs and take alternate action. Like, as soon as Ozaki got the idea that the infectious disease is vampires, he instantly went from thinking in terms of science to thinking in terms of myths and legends (although his approach to getting the Shiki was still very systematical--scientific method ftw). Also, it was (relatively) easy for him to get past his society's teachings that murder is wrong and stake the vampires anyway. Granted, he didn't see them as human so to him it's not murder, but they look human and they act human (Kyoko did). What I'm trying to say is that it's easy for him to abandon the way of thinking he grew up with in favor of another one that fit the circumstances.

Whereas Seishin, although rejecting the system, clings to the idea of murder being wrong and initially doesn't buy Ozaki's idea of there being vampires. His agreeing to stay up with Ozaki and watch Setsuko indicates his deep friendship and trust in Ozaki more than anything else. I mean, if my doctor friend asked me to stay up in a dark, creepy clinic with him all night, I'd do it because it would be fun to bring a video camera with and film a homemade horror movie, Paranormal Activity-style (can you imagine the Wakas doing that?). However, Seishin's obviously not there for fun. Although he rejects the system more actively than Ozaki, he clings to it more tightly once circumstances start deviating their paths from the system.

To be honest...I don't know enough about Gene's character in general. I mean, I know that every time "Naru" appeared in Mai's dreams it was actually Gene, but I haven't gotten to the part where he's actively discussed. I just read the part of the LN that takes place by the lake where Gene drowned, but not even the whole of that novel. Now that you mention it though, Gene does seem shady in not correcting Mai, although I could think of a few reasons why that is. Perhaps he didn't want to confuse her when there were more important things at hand (most of the time when he appeared, she was in some sort of danger, right? Not the best time to reveal the fact that he's Naru's twin). Or maybe he thought she was a good match for his brother and wanted her to start thinking of Naru in "that way"--the first time Mai started having romantic feelings toward Naru was after Gene appeared to her for the first time, if I recall correctly. So theoretically, by smiling in Mai's dream, having her think that it's Naru smiling, he's showing her that Naru can make that expression too and that he's not as cold as he seems. That's right, Gene is the captain of the NaruxMai ship.

...Yeah, I could imagine an indifferent Ozaki. Very well, actually. I can imagine him getting a job in another hospital acting like nothing happened in Sotoba besides a fire. Since he can't change anything, there's no use dwelling on it, right? I feel like that was also his attitude toward Sotoba. Like Seishin, he also likely found it suffocating and frustrating and lonely, but he couldn't change a whole village system that's been in place for generations, so why worry about it? Even so, I know that bottling up your feelings over time just makes anything worse, no matter what your personality, so in this case Ozaki's skill of being able to act like something's not a big deal would work against him.