Writer has put his back on the wall with this. If he doesn't reject sayu the story needs 100+ chapters to become wholesome, it will become kimi no iru machi. Also if u wanna be realistic, if a friend of yours tells u, i like this girl, you would back off, it's not some fate bound love. Also I don't like the deus ex machina sort of role that they are giving to senpai. It's stupid considering she is eyeing him as well.
The only decent way out, is if the mc yolos/forces something with fuyuki using the bracelet as an excuse to lvl it up a bit, so that he actually gets a reason to reject sayu.