If I could suggest something off this, I think it would help if the default face for the male character better illustrates this intention? Because the default face is pretty boyish compared to the body, and the male expressions don't particularly give an "adult" impression on their own.
With the previous art style the defaults looked roughly the same age, but when the default female is a young high school student at best, I think it's understandable folks would assume the male is intended to be the same since there doesn't seem to be anything suggesting otherwise.
So, hrm. Possible solution: Maybe make the default hairstyle balding or something?