I felt the same way in the past. I have also been on a lot of online forums and also some fanfiction sites, and it was hard for me to reach out to people or leave comments. Once I started, people were certainly receptive to talking, but even if they did respond, that didn't guarantee friendship. I guess what I am trying to say is to just be active in commenting (like the person ^ said) on things that you like because friendships, for me at least, usually start with being mutually excited about something and from there, having certain similarities in interests. It's hard, but it's certainly worth doing!
On another note, I assume you're on this site because you like anime/manga/games/Japanese culture and I am also new around here, so I'd be happy if we could talk too!