I think a tag for all those living/playing/transported in a RPG world works would be useful (for me, to read them all ).
Examples that would receive the tag:
http://vatoto.com/comic/_/comics/the-gamer-r9967
http://vatoto.com/comic/_/comics/in-another-world-im-called-the-black-healer-r16801
http://vatoto.com/comic/_/comics/netgame-no-yome-wa-onna-no-ko-ja-nai-to-omotta-r14204
http://vatoto.com/comic/_/comics/toaru-ossan-no-vrmmo-katsudouki-r12453