1) This fish was either dead or dying.
2) Sure, Hana eventually fell in love (and by "eventually", I mean "lightning fast"), but at the point Ap decided to marry her, Hana had no idea whatsoever what was happening. I mean, at least establish basic communication before dragging her to the oltar, so at least she knows what the deal is...
3) This page pretty blatantly says Hana will come back after fulfilling her dream (she must have dodged the no-dating clause in her idol contract, heh), so overall, the end was not as sad as the comments here led me to believe. Still, an actual sequel would be nice.