Asakusa Demon

The Asakusa Demon is a minor character in Demon Slayer: Kimetsu no Yaiba. He was a pedestrian in Asakusa who Muzan Kibutsuji turned into a demon.

Appearance
The Asakusa Demon was once a man with ordinary features: average height, fair skin, short black hair and black eyes. He wore a gray-green haori over a deep indigo kimono and a grey hakama. After being turned into a demon, his irises turned dark red and there is a white glow around his reduced pupils.

Asakusa Arc
One evening, as the man strolled with his wife along a bustling street in the vibrant city of Asakusa, they unknowingly walk pass by Muzan Kibutsuji, Rei and their daughter. Muzan reaches behind and quickly scratches the man's neck with his sharp nails. Tanjiro Kamado is the only person witnessing the incident. Blood immediately spews from three deep gashes in the man's neck. He stops walking and grabs his neck in pain. Seeing him pause, his wife asks him what is wrong, but the man keeps his head down while Muzan's blood starts spreading through his veins.

Gritting his teeth, the man then turns into a demon. Tanjiro tries to reach forward, but fails as the man begins attacking his wife by biting her shoulder. The wife screams in horror and all bystanders watch in shock. Before he can further injure her, Tanjiro manages to tackle him and pull him away from his wife, then gags him with a scarf to prevent him from biting anyone else. His wife was still concerned about her husband, but Tanjiro tells her to use a cloth to press down on her wound, while he keeps pinning the struggling husband down.

As Muzan leaves the scene with his frightened wife and daughter, the authorities arrive at the scene and order Tanjiro to release the man immediately, not knowing his demonic nature. Tanjiro pleads with them to not interfere, not wanting the demon to harm anyone else. The police ignore him and try to pull Tanjiro off. Entering the scene, Tamayo uses her Blood Demon Art to blind the police from seeing Tanjiro. The couple are taken back to her house, where she treats the wife's injuries and has the demon restrained in a basement.

Swordsmith Village Arc
In a letter to Tanjiro, Tamayo writes that by using blood samples from Nezuko Kamado and several Twelve Kizuki demons that Tanjiro provided for her, she was able to synthesize an antidote for turning demons humane. She tested this antidote on one of Muzan's victims, the man from Asakusa. He successfully got his consciousness back and now lives free of Muzan's influence on a small amount of blood.

Infinity Castle Arc
When Muzan was caught in the massive explosion that was caused by Kagaya Ubuyashiki blowing himself up, he tries to regenerate but flesh seeds appear around him, which suddenly burst into giant black bramble branches, that Muzan recognizes as a Blood Demon Art. The branches in the shape of spikes do not cause any permanent harm, but do immobilise him for some time, as he needs to absorb them to escape. Tamayo then appears and stabs her hand through Muzan's stomach. She reveals that the flesh seeds Blood Demon Art belongs to the man in Asakusa he turned into a demon.

Blood Demon Art
Flesh Seeds (の) - A Blood Demon Art that creates miniscule seed-shaped flesh which then protrude giant spikes in every direction, used to pierce the targets body and restrain them. Once inside the body, the spikes continue branching out in the target's flesh, making them hard to pull out. Multiple seeds can be created at once, and seemingly materialize in thin air. This ability was powerful enough to restrain Muzan Kibutsuji for a short amount of time.

Trivia

 * Other than Tamayo, Yushiro, Chachamaru and Nezuko, he is the only other demon free of Muzan's influence and able to survive without eating humans or beasts.