After the Mugen Train mission and the death of Kyojuro Rengoku, Tanjiro, Zenitsu, and Inosuke continue their training. One day, they encounter Tengen Uzui, the Sound Hashira, who is searching for young women to help him with a mission. After some arguing and confusion, the three boys end up joining him. Tengen reveals that his three wives—Suma, Makio, Maomao and Hinatsuru—were sent into the Entertainment District to investigate reports of a demon. One by one, they stopped sending information back to him. To enter the district unnoticed, the boys disguise themselves as girls and are placed in different houses. Tanjiro adapts surprisingly well and quietly gathers information from workers and residents. Zenitsu struggles with the situation but pays close attention to what is happening around him. Inosuke is impatient and immediately begins searching for hidden passages and suspicious activity. As they investigate, they hear stories about women disappearing without explanation. Strange rumors spread through the district, and everyone seems afraid to speak openly. The boys begin to realize that a powerful demon may be living among the courtesans. Tanjiro notices that some people become nervous whenever certain names are mentioned. Zenitsu senses that something is wrong with the atmosphere of the house where he is staying. Inosuke, using his keen senses, discovers unusual spaces and hidden routes that suggest something secret is happening behind the scenes. Meanwhile, Tengen continues his own investigation. The clues left behind by his wives suggest that they uncovered something important before contact was lost. Rather than finding simple answers, every clue leads to more questions. The tension increases as evidence points toward a demon who has been hiding in the district for a long time. The demon is clever, patient, and powerful enough to avoid detection. The missing wives are not simply lost—they have become entangled in the demon's plans. Eventually, the investigators learn that at least one of Tengen's wives is still alive. This discovery gives them hope, but it also confirms that the enemy is nearby. The mission changes from gathering information to preparing for a rescue. By the end of this part of the arc, the mystery is far from solved. Tanjiro, Zenitsu, Inosuke, and Tengen understand that they are facing a dangerous opponent. The search for the missing wives becomes the beginning of a much larger battle that will reveal the true demon controlling the district.