I don't know from Battle Royale, but I will point out that I have known girls like Miss Nakagawa - mousy, innocuous girls who simply don't leave a deep impression on the texture of reality.

I can readily imagine that such a girl could be very attractive to someone with a flamboyant or violent lifestyle, simply because she is so... restful. He knows her, he can trust her, she needs him and [presumably] does what she can to show her appreciation, even if she can't think of much that would show it...

Yes, I could see a man turning away from neurotic, violent, faithless but more 'interesting' women, to favor such a gentle mouse.

I would, without question.