I’ve read the two light novel volumes currently available, and honestly I think Yua and Fukusuke should end up together. Right now they clearly have mutual feelings, so that pairing just feels the most natural.
It would also get pretty messy if Amari ended up with the MC, especially since she already knows how both her best friend and Fukusuke feel about each other. Because of that, I feel like Amari and Fukusuke are better off staying friends rather than their relationship turning romantic.
If Amari does end up with someone, I think Fujisaki (the basketball friend) would make more sense. That way the relationships don’t become unnecessarily complicated.