Tengai Retrogical

 is a Japanese manga written and illustrated by Rin Asano. The manga was licensed in the US by ADV Manga. As of March 2009, Mag Garden has released 7 "bound volumes" of the manga.
Reception.
Mania.com's Mike Dungan described the manga as "a very enjoyable story that is equal parts action, horror, fantasy, science fiction, historical drama, and comedy." He commended the manga's characterisation, stating there was an "air of confidence in both the art and the storytelling".