I was very disappointed with Touya, for his hatred of his parents to be stronger than his loyalty to Takanari. Tsk. And also annoyed at Shizumasa for interrupting such a romantic scene. T_T
I'm really made at Shizumasa for his attitude, but I can't hate him that much just yet... because, honestly, we haven't really heard his story yet, only Takanari's, so it's unfair to issue full judgment against Shizumasa.
I personally don't think the book is a stupid reason to finally choose, though. In the very beginning, Haine fell in love with the book's author (dunno how one does that, but that's beside the point), and confessed that love to the person she believed to be said author, Shizumasa. But, it was really Takanari. So, the person she had really fallen in love with from the start was Takanari... meaning that, compared to the book, and all the time Takanari and Haine have spent together since high school started, Shizumasa's only merit was what he did for her when she was a delinquent. Outside of that, all her feelings had developed toward Takanari, so it makes sense that she'd choose him.
In regards to that snowy night... Shizumasa stated that he had taken that love confession very seriously and had been thinking about it all those years and hadn't forgotten her at all. This is one of the things that bugs me the most about him... he knew perfectly well that it wasn't really him that she'd fallen in love with, but he accepted the confession as if it was, because to him, Takanari truly is just a "shadow" and that everything that was Takanari's was automatically Shizumasa's (and that Shizumasa's rights to it came first). Really ticks me off, that attitude. And getting so possessive over Haine because of a confession made in their early childhood doesn't seem too reasonable either. Takanari, however, has received more than one confession since high school began (though I would only count the second one, when Takanari was sick, as truly being directed toward Takanari).
So, I wonder... when is she going to stop calling them both "-sama"?? XD
( That post was probably longer than necessary... >_> )