Yea i noticed the romance the time i reread it too. The scene that got me thinking that the ML really has feelings for nunnaly is the part where he said smthn about a law or smthn and the story behind that law was talking about a nobleman liking a commoner and he did/implemented that law because he wanted the commoner woman he likes to be happy and free. Just from this scene, my mind got me thinking that alves, a nobleman/the ML himself, likes a commoner and the only commoner he is close to is nunnaly. Like they literally see each other everyday at school. There are a lot of scenes and chapter that really strengthened my belief that alves really is in love with nunnaly.
The first time I read this I thought it was just like those rivalry friendship thing, the second time I read this I finally understood there were some romance. I don't know how many times I've reread this but now I can see he has always been in love with her. Remember the mirror extra? We can see that he got distracted cause she giggled and he said brown eyes and stuff like that so my speculation is he fell in love with her at first sight and that's where the sudden rivalry sparked and you can get the rest lol