Tanjiro ventures to Asakusa, Tokyo for his second mission with the Demon Slayer Corps. The big city of Tokyo is new to the village boy. He is to track down a Demon disturbance in the area, but early into his assignment, Tanjiro notices an all too familiar scent. He frantically rushes into the crowded streets and discovers Muzan Kibutsuji masquerading a human with a family.
To escape the situation, Muzan transforms a man into a Demon and flees with his family as Tanjiro deals with the new demon. This gains the attention of Lady Tamayo and a young boy named Yushiro. They dispell the situation and bring Tanjiro back to their secret house where Tamayo, a Demon doctor, treats patients. Yushiro is a demon as well, and they're trying to eliminate Muzan.
Meanwhile, Muzan is enraged by Tanjiro's appearance, reminding him of a similar Demon Slayer from the past. He orders two of his followers: Susamaru and Yahaba to bring him Tanjiro's head.
Tamayo and Tanjiro agree to help manufacture a cure for demons by studying Nezuko's blood and the blood of demons close to Muzan. Lord Muzan's assassins interrupt the meeting, claiming to be members of the Twelve Kizuki, and unleash a furious assault on the house using Temari and Arrow spells.
Tanjiro takes on the Arrow Demon while the others play a deadly game of handball with the Temari Demon. Tanjiro is able to eliminate Yahaba by combining multiple Water Breathing forms, but he's exhausted from the fight. Nezuko and Yushiro are able to hold Susamaru off, but she's ultimately too powerful for them.
In order to stop the situation of escalating, Tamayo uses a spell that triggers Muzan's curse inside Susamaru. The Temari Demon falls victim to the curse and dies, leaving a scarred image in Tanjiro's head.
After the battle, Tamayo and Yushiro decide to leave the area. Nezuko sees them both as her human family, moving both Tamayo and Yushiro. They bid farewell and Tanjiro leaves the city for his next assignment to the south-southeast.