He remains her bitter rival until the graduation.
That said, he isn't given any preferential treatment, and in fact the two's constant fighting become such a common scene that this one time they get into a fight on the day of school vacation, the teachers just shouted "Go back before it gets dark" and returned to school.
On the graduation dance he did soften up a little bit, with the whole mid-air dance with just the two of them in the garden (although it seem to be heavily implied that he was sent to her with some kind of 'go to your fated person' magic)
Heck, he even went as far as making a formal pose and said "O beautiful ice witch, will you honor me with a dance?"
(though that scene ends with the two getting back to the track of "I'm definitely going to defeat you one day!" "O RLY? *smug*")
That said I stopped reading after the school arc was over so I don't know if he ever soften up anymore than that.