Unfortunately I'm in the situation where if they want to talk to me, they have to grab me before I leave the room (often with the Korean co-teacher telling me to go with her) or they have to come to me in the language teacher's office - not great for the shyer students. Plus the more confident ones who do come to talk to me often get shooed out after a while by the head of department.
I'm not a fan of One Piece myself, despite almost everyone else I know loving it. Maybe between Naruto and Death Note I can cover most of the anime fans of both genders. 
Ah. I have my own classroom, the "English Zone", so students come to me. Also, this particular student has a class that happens before lunch, so we both usually lose half our lunch break talking about anime. But, usually when students want to talk to me, no one shoos them away or anything - my co-teachers are usually already gone by that point! I guess there is a benefit to being in an office by yourself (it can be great since there is no one to scrutinise my every move. I get enough of that at lunch!)
I'm also not the biggest fan of One Piece (I've only seen around 50 or so episodes), but I've seen a lot of other stuff that my girls are familiar with. In one lesson, they were drawing their opinion of what the "perfect boy" would be like, and one group ended up drawing a picture of Kazehaya Shouta from Kimi ni Todoke, a very popular shoujo (girls) romance. They were beyond impressed that I knew his name
I have another girl who sometimes reads manga before class, and again, she is so impressed when I'm familiar with series like Kuroshitsuji, Fullmetal Alchemist and Trinity Blood.
At this point, I'm considering using manga in class, maybe to teach some basic genre and do a fun writing activity.
