ITS NOT CHEATING

Doesn't make one bit of difference whether he was a sex worker or not (which he wasn't, since he was repaying his benefactors not them paying him) or whether or not they were technically in a relationship. The fact that Yuu obviously had expectations (as seen when he smelled the perfume on Aya and thought it would be good to create some distance between them because of it) that he would only have sex with him and had no idea about this supposed 'work' Aya was doing is what makes it cheating. Aya never apologized for that, instead victim blaming Yuu for it. Sad. KT.