Rumia is a youkai with the ability of manipulating the darkness. She first appeared as the Stage 1 boss of Embodiment of Scarlet Devil. Rumia, in a sense, represents a very basic idea of a "youkai". She does very little with her life and spends it just trying to hunt and eat humans, and even then, she doesn't really want to do that all the time. She is rather simple-minded and really doesn't serve an overarching role in Gensokyo aside from being a typical youkai feared by humans.