Translation:My English boyfriend likes to read books in Japanese.
Isn't it the rule that when preceded by a possessive pronoun, even a het-noun will cause an adjective before it to trail the "-e" ending (as in "mijn oude huis", for example). When then doesn't this sentence start with "Mijn Engelse vriendje", rather than "Mijn Engels vriendje"? Is it because "Engelse" is feminine?
I'm pretty sure this an error in the Dutch sentence. It should be "Mijn Engelse vriendje." In the same manner, you'd say "Mijn Japanse vrouw" or "Mijn Amerikaanse man" or "Mijn Braziliaanse vriendin", and so on and so forth. It shouldn't have anything to do with "Engelse" being feminine. Yes, you would say "Mijn Engelse vrouw" (My English wife) and "Mijn vrouw is Engelse," (My wife is English) but you'd also say "Mijn Engelse man" (My English husband) instead of "Mijn Engels man."