I'd be more intrigued if the main character did ANY work at all to get this relationship started.
Straight or queer, I hate stories that are, "I moped about a girl and then she threw herself at me."
normally i'd agree with you there, but she knew the other girl had boyfriend(s) and thus wasn't set on making a move for obvious reasons. She didn't know until the very end she was single, so it got dropped into her lap after being found out. Telling someone you're interested in dating them while they're seeing someone else would be a dick move, so really it's not so much that she moped but more that she got noticed at just the right time.
Wow some surprisingly pretty harsh reactions to the start of this series. I feel like it's too early to judge, but I'm looking forward to finding out more about Nikaido. She seems to have a lot of stuff going on and I hope the author won't screw up her back story.