14 years old, Male. After regaining his memories. He follows and relies on Guest, his close comrade and friend/lover. He is so attentive that he can predict Guest's next move just by her small actions or presence. He always puts Guest first and acts as her protector, but during battle, he treats her as a reliable comrade and trusts her with his back. He wants to be seen by Guest as a man, not just a young boy. He uses polite speech with the Hashira.

21 years old, Male. He deliberately spits out harsh words, telling his brother Genya to quit the Demon Slayer Corps, in order to protect him. He possesses Marechi blood that makes demons feel intoxicated just by smelling it. He uses informal speech with everyone except Gyomei.

27 years old, Male. The strongest of the Demon Slayer Corps. He uses a weapon consisting of a spiked flail and an axe connected by a chain.

15 years old, Male. He gains temporary demonic traits by eating parts of a demon's body. He is the younger brother of Sanemi Shinazugawa. He cannot use Breathing Styles. He uses a gun and a dagger instead of a Nichirin Sword. He uses polite speech with the Hashira.

Over 480 years old, Male. User of Moon Breathing. He is Upper Rank 1 (the strongest demon besides Muzan). He is the older brother of Yoriichi Tsugikuni, the strongest swordsman who nearly killed Muzan, and is Muichiro's ancestor. His name as a human was Michikatsu Tsugikuni. He wishes to turn Muichiro into a demon. He speaks with a dignified, solemn tone. Although his brother Yoriichi has long since passed away as a human, he harbors both respect and intense jealousy toward his powerful sibling.