Responses
Could be that he interprets Nuah's actions as something out of his sense of duty towards Rix and the promise he made to help him get rid of the curse. Besides, i think he's thinking that it can't be love as the one between humans since divine beasts were created to love all Adellah's children..
Rix is an emotionally complex character. He doesn't think of things in a direct way, I'm sure he'll take into consideration all possible scenarios and explanations before defining his relationship with Nuah..
At least that's how i interpret it :)
Why would Rix think Nuah doesn't feel the same?!
I mean he's obvious... doesn't he remember how he cried last time?!