Yeah, its pretty obvious buttt I think thats exactly how this story is supposed to be. I think they both still don't "love" eachother. Kei loves sano because he want to make people happy and sano loves kei because he's a fan. They don't really love eachother as a "person" at first. And then as the stroy goes on we see how they actually fall in love with eachother while they are dating, learning eachothers personalities and their true selves beyond just being an idol and a fan(▰˘◡˘▰)

This is adorable don’t get me wrong but it feels as if kei doesn’t really like him romantically. Just seeing the mc as a goal to accomplish? He only proposed because he liked making people happy and by marrying his biggest fan will he make them happy forever. But thats it. Like thats his whole life goal. Nothing like, I fell for you after seeing how dedicated you are. He just there yk? No romantic interest or feelings from the start of their relationship.