The Flute Demon takes the appearance of a very elderly man with wrinkly skin, and very long black downward-slanted eyebrows He has long slanted eyes with black scleras similar to the Serpent. Flute Demon is murderous and disdainful of humans, happily displaying the corpses of Demon Slayers he had killed and taunting Kyojuro Rengoku by claiming he can join his fallen comrades in the afterlife. This demon also has no official name in demon slayerso I'm using the romaji for him which is : fue oni