A Skeleton is a common type of undead enemy.
Skeletons appear as enemies.
There are also skeleton enemies called Yari Gaikotsu.
Yari Gaikotsu (槍骸骨 "Spear Skeleton"?) is an enemy that appears in the second stage, "Kugyō no Michi", and the third stage, "Yūkai". They aren't present in the Famicom version of the game.
Several Gaikotsus from Genpei Tōma Den and Yari Gaikotsus from Shadow Land appear as enemies, alongside the Skeleton Murderers (Death) from Capcom's Ghosts 'n Goblins series. These skeletons are habitants from the Makai.