I think Ai will hate him for causing the death of her sister,but after she'll see that he's a good person,she'll probably forgive him,and respect him...Which is why I would love to see them together,because there would be an evolution in their relationship...
I would hate to see Ai falling for him quickly(that would be OOC for Ai),but if she learns to know him more,that would be a cute couple.I don't see anything wrong with them being together,if they take the time to know each other.
And I'm pretty sure they were close in the past,so I have a little hope for this pairing^^