"I'll wear these cute clothes so my boyfriend thinks I'm cute"
"That's very cute"
Blushes profusely
Are Japanese people just incapable of reacting normally, you've been together for a while at this point why are you still reacting like you've just started dating? I wouldn't get annoyed if it wasn't such a common trope.
at least in the honeymoon phase of relationships, it's very... drastic of a change from the rest of society. Because of how rigid and prudish Japanese culture normally is, outside of specific circles and situations.