The series was adapted into an original video animation produced by Anime International Company (AIC), and an anime series which aired from 2005 to 2006. Additionally, AIC has developed two OVAs and a film, and OLM, Inc. has also developed an anime series as well. Companies have developed thousands of types of merchandise, such as video games, and a light novel. The OVA was licensed by AnimEigo, while the film was licensed by Geneon Entertainment, and the various TV series were licensed at various points by Media Blasters, ADV Films and Funimation.