GetsuFumaDen is a series of action-adventure, 2D platformer games by Konami which feature a heavy emphasis on Japanese mythological themes, especially regarding the Underworld and its demons. There are only two main titles in the series, which span over a long hiatus of 34 years between the first entry, GetsuFumaDen from 1987, and the second one, GetsuFumaDen: Undying Moon, slated for release in 2021-22.
The heroic protagonist of the first game is Getsu Fuma, descendant of an ancestral bloodline of fierce warriors belonging to the Getsu Clan. He ventures into the depths of Hell in an avenging mission due to the loss of his two older brothers at the demons' hands. He does this by making use of very advanced forms of martial arts, which include the use of his trusty Hadou katana, shuriken and bombs, as well as the use of magical inner energy which he uses to defeat those unearthly monsters that dare to stand in his path.
While for a long time a sequel wasn't made after the first game, several GetsuFumaDen-based stages appeared in other Konami games. These stages are always set in Hell and appear in Konami Wai Wai World, Wai Wai World 2: SOS!! Parsley Castle and Castlevania: Harmony of Despair.
In 2021, 34 years after the first game, a sequel was announced titled GetsuFumaDen: Undying Moon. The story takes place 1000 later, when the antagonist of the first game, Ryukotsuki, manages to break the seal cast by the first Fuma and once again seeks to conquer the surface world. The protagonist of this new adventure is also named Getsu Fuma and is the descendant of the original. As his predecessor, he also ventures into Hell, now in search of his lost brother.