I've successfully sold Japanese manga via a local ad site. There isn't really a Japanese comminity in my city, and all buyers were locals. I believe they were mainly fans of the titles, who saw extra value in the manga being Japanese, regardless of whether they were able to read them or not (I do remember some of those who picked them up F2F telling me they don't speak/can't read Japanese). While I did learn some Japanese and bought Japenese manga mostly to try to practice reading, I do admit that today, 15 years after abandoning my Japanese studies and never finding a way to get back into them, I would still buy some titles in Japanese because I just like the look and feel of Japanese mangas, and of course, there's always the possibility to get back into my studies once again.
I also had some success selling with the help of a local comic book store who (back then) offered the possibility to keep your items on their shelves, and if they sold they gave you the price (deducting a small fee). It might be worth checking out if there's a shop near you who are willing to do this - I remember I was happy with this because while on an ad site you mostly only find something if you look for something, here it was there for everyone to see, and in addition, the books (and other stuff I gave them) weren't taking up space in my apartment ^^