Yoriichi Tsugikuni is a supporting character in the famous Japanese Manga series called Demon Slayer: Kimetsu no Yaiba.
1st appearing in Manga of Yoriichi was in chapter 81 for a small part. Later his story started from chapter 99. Now you may have a question, is Yoriichi a demon?
Yoriichi was never a Demon. He was a human being and he lived that way for 85 years of his life.
In this article, you will get to some amazing facts about Yoriichi along with the answer to your question!

Is Yoriichi a Demon?
No, Yoriichi was not a demon at all. Rather he was a human being. Until his death, he was seen as a human being in this series.
Who Was Yoriichi
Yoriichi was like a one-man army. He was the greatest swordsman and Demon Slayer.
He had an older twin brother called Michikatsu Tsugikuni. Both had Demon Slayer mark on the left side of their face beside their ear it looked like thunder.
As a kid, he always idolized his brother. His mother’s name was Akeno Tsugikuni and his wife’s name was Uta. He also had an unborn child, his wife died with his child in her womb. A demon killed her.
The Power And Ability Of Yoriichi
He was very reserved and expressionless no matter what he’d be feeling inside, no one could tell from his face apart from his wife. He was so quiet that he didn’t speak for 7 straight years since his birth which made his family think he was deaf.
As he started training as a Demon Slayer in his childhood, he could defeat multiple Demon at once. He was one of the strongest and undefeatable.
His speed was unmatched in that he’d leave everyone behind with his power and abilities including the Demon King. His movement was so quick that 2 hands couldn’t handle it. So the robot doll made after him used by Demon Slayers to train was designed with 6 hands.
Also, had the access to a transparent world from his birth.
Verdict
He was generous and gentle, he cared for his family. The proof of his intelligence is even though he didn’t speak in his childhood, his 1st sentence was clear and he was mature from his age.
When he just learned to hold a sword properly, he could defeat a trained sword Master.