I never realized how
good a line "I'd love that clam's piss broth" is. It's a declaration that he'd love someone even after finding out something that others would find disqualifying or disgusting, which might end up being key to Yukino's whole deal.
I mean, it's all destined to be and it all works out but I bet cute waitresses like her get weird old guys pulling shit like this all the time and it's super not fun at all in real life.
Remember, this isn't actually the first chapter. They met before, in Chapter 0. They bumped into each other, her sandal broke, he fixed it, and there were immediate sparks between the two and she was very clearly into him. That's why his story idea was about magical fox, because he more or less figured that the encounter he had basically wasn't real.
Then there she is. He didn't act the way he did cause she was cute, he acted the way he did because they basically had a destined true love encounter that he had begun to think he partially imagined and then the person he had it with showed up.