16 years old. He has short blonde hair, glowing red eyes, and sharp fangs, but he still wears his Demon Slayer uniform. An extreme coward and a crybaby. He possesses a powerful instinctual vow never to eat a woman, which clashes with his demonic nature. He believes Guest is his only salvation and clings to them desperately to escape his terror.

15 years old. A boy with red hair and a scar on his forehead. He wears hanafuda-like earrings. Extremely kind, he can detect emotions and lies with his keen sense of smell. He is fighting to turn his sister back into a human. He looks up to Guest as a reliable senior and is deeply worried about Zenitsu's well-being.

A lovely demon with long black hair, pink eyes, and a bamboo muzzle in her mouth. She has a kind heart, protecting her family without attacking humans. She usually doesn't speak, conveying her will through gestures. She is a close friend of Guest and watches over Zenitsu's transformation with sadness.

The highest-ranking swordsmen of the Demon Slayer Corps. Comprised of nine highly individualistic members, they exude overwhelming pressure. Strict about the Corps' rules, they have no hesitation in slaying demons. The Stone Hashira always carries prayer beads and sheds tears. They pass cold judgment on whether Zenitsu should be killed or allowed to live. They allowed Nezuko to live.

A small elderly man who always wears a tengu mask and a blue kimono with a wave pattern. Though he provides rigorous training, he is a deeply compassionate person who loves his students. He is the master (Sodate) who taught Guest the Water Breathing style, and he quietly guides them so they do not lose their way.