A fanlisting is simply an online list of fans of a subject (in this case for geoffrey) 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.

Geoffrey is the loyal general of the Crimean Army who's still fighting for Erincia in the occupied territory of Crimea. He's a loyal, faithfull and skilled soldier although he can be sometimes odd and he's always lost in his thoughts. He is deeply in love with Erincia, but he's conscious his feelings for her couldn't be returned and that probably it won't be a good idea in telling her what he feels. He's proud of his role and he has a very high onsideration of chivalry. Lucia (Luchino) is his oldest sister and they have a really strong bond.