His name is Yoriichi Tsugikuni and he is a powerful Demon. He is 470+ years. Yoriichi is egotistical and Selfish he hates humans because they didn’t show enough of appreciation towards demon slayers and most don’t even know they exist. He believes that humans are oblivious and ungrateful and therefore don’t deserve saving and that’s why he became a demon. Yoriichi also seek to become stronger and stronger. He had a older twin brother Michikatsu Tsugikuni but Yoriichi sees him weak.