A fanlisting is simply an online list of fans of a subject (in this case for Leon Magnus) that is created by an individual and open for fans from around the world to join.
There are no costs, and the only requirements to join a fanlisting are your name and country. Fanlistings do not have to be large sites (although some are), they are just a place where you can sign up with other fans. TheFanlistings.org is the original (but not official) web directory for fanlistings, dedicated to uniting the fans.
Description from TFL.

Natasha is an healer escaping from Grado and chased by the Emperor's Army for of course political reasons (especially because she knows part of the truth concerning the obscure plans of her sovereign).
She might appear as a weak person, but instead she faces difficulties with her delicate attitude. She's willing to know more about those that accompanies her, still she's somehow shy and she tends to skate over personal matters.
She makes an extremely cute couple with Joshua.