1) It's not because he "doesn't want to" but "why he doesn't want to". Basically "he likes her not as sister" kind of deal.
2) He was beaten for trampling over her feelings. Without even realising it.
I love the ability to portray a character that is without question monster, while still being powerless human and sympathetic protagonist to boot. The singularity of paradoxes.
I was holding on reading this series for a while and I forgot how brilliant it is.
Sudden side story is great.
Sudden side character input is great.
Sudden coliving is great.