The Flute Demon takes the appearance of a very elderly man with wrinkly skin, and incredibly long black downward-slanted eyebrows. He has long slanted eyes with black scleras similar to the Serpent Demon with the traditional fangs of a demon.
His attire consisted of a flower-patterned robe tied to one side by a white ribbon and long white sleeves with a thick black frame at the end. He has long black hakama pants similar in appearance to the Demon Slayer Corps members with geta shoes. As well as this, he wears a black Japanese saggy cap with a tassel at the end.
Not much can be said from the Flute Demon's personality other than he has been shown to be fairly arrogant when he believed that Kyojuro alone as reinforcements wouldn't be enough to defeat him. Along with this, he also has the incredibly sadistic and homicidal perspective of a demon as he only focused on his victims going to "hell" as well as him having a joyful attitude on horrible situations such as him sucking out internal organs of multiple children and murdering multiple Demon Slayers in front of them.
Due to him being able to easily evade Kyojuro's first attack as well as him killing nine Demon Slayers, he was incredibly powerful compared to the average demon. In addition, due to him stating that he would soon join the Twelve Kizuki, it can be assumed that his strength is near equal to that of a Lower Rank.
Flute Manipulation: The Flute Demon's main ability is to conjure a special flute that when played, enacts various effects.
- Nervous System Disruption: When his flute is played, it disrupts the nervous system of his opponents (if they try move one of their feet, their head will move instead, if they attempt to move one of their hands, their feet will move, etc.), thus making it nearly impossible to accurately move.
- Wolf Manipulation: This demon can also use his flute to summon 2 black wolves and command them to kill his opponents. It is unsure whether he can summon more than 2 demonic wolves.
- (To Kyojuro Rengoku) "My dogs will devour you... as you wriggle like a filthy worm!"
- (Last sentence before death) "No!! I was going to join the Twelve Kizu..."