itch.io

You raise heart meter by going on dates, but star bar (the actual determinant to your love status) is increased by weekdays spending time scenes (it increases when you get important events). Maybe you went mostly on dates and didn't spend time with him on weekdays much? 

(In my sister aka beta tester's last playthrough, she got to woo Tocchan by mid March bcs she got all the cheat enabled, so no need to fuss with raising stats etc)