Exactly so, it's a tit for tat kind of thing they have going on. And I for one, enjoy Nunnuly and Alves's banters.
Alves says so himself in the previous chapter that he doesn't want Nunnuly to bow down to him and got annoyed when she was being all formal to him as if she was below him. He sees her as his equal.
Alves likes Nunnuly but they have different social statuses . Back in some chapter when they were talking about the laws , I take it that it's really hard for nobles to marry people outside of their social status (especially commoners). And Alves is a Duke's son and a prince's cousin, a direct relation with the king at that. Just how hard would that be (to establish a relationship with a commoner) for him.
An action like from someone so high up in the social ladder will most likely be frowned upon by the majority so he's obviously holding it back for both his sake and Nunnuly's and either slowly trying to close the relationship between them or is trying to rid his feelings of her so that no one will be hurt in the process.
To be honest, I feel like most of the commenters here when they started reading this first they already labelled Alves as a jerk to them. And being stubborn and not wanting to let go of that and say that they were wrong , make more accusations of him in an attempt to convince themselves that what they're saying is right. Sure he was a jerk at first but he's improved so much in one volume. Not paying attention to most of the story and say he's a jerk. It's really sad when that's also how it is in real life. ; - ;
You're right,Nunnuly isin't made out of glass. She's a strong woman! Not seeing eachother as a weak being that needs contant protection and seeing the capabilites in one another and trusting them to have the ability to do what needs to be done. That kind of relationship is more appealing. Alves does not look down on Nunnuly and her abilites and, Nunnuly sees Alves as a capable but rival friend sort of person. From the LN, this part of Nunnuly's pov strikes me a lot
" When Rockmann conjure flames I would freeze them, and should I conjure ice, Rockmann would melt it. One step forward, one step back, I could ask for no wortheir opponent. "
(PS I recommend checking it out, it's written really well.)