Yoshiwara

Yoshiwara is a district located in Tokyo, Japan, and it serves as the main location of the Entertainment District Arc. It is a red light district, a location with a high concentration of prostitution and sex-oriented businesses.

History
Yoshiwara was founded in the Edo period of Japan, where it quickly became a prominent district for prostitution and sex work. The highest ranking courtesans were known as Oirans. Three of the most famous and prominent pleasure houses in the district during the Taisho period were the Tokito House, Kyogoku House, and Ogimoto House.

For nearly a hundred years, before the latest intervention of the Demon Slayer Corps, Yoshiwara became the home and lair of two extremely powerful demons, Upper Rank Six of the Twelve Kizuki in the siblings Daki and Gyutaro. Owing to Daki's great beauty, experience in sex work, and her unique Blood Demon Art, they made Yoshiwara a successful hunting ground, where they captured and devoured numerous victims. Daki's long life and subsequent attempts to hide her true nature started the legend of a very beautiful but cruel Oiran, the stories passing down generations. Most attempts to stop them by the Demon Slayer Corps were unsuccessful, with Gyutaro claiming to have killed 15 Hashiras, and Daki killing 7.

Assigned with discovering the demonic presence in Yoshiwara, Sound Hashira Tengen Uzui tasked his three wives, Hinatsuru, Makio, and Suma, with infiltrating the three most prominent houses and looking for clues. When all three suddenly stopped providing him with information, he began his own intervention to save them and find the demon.

Plot
Tengen attempted to take Aoi Kanzaki and Naho Takada as he needed female Demon Slayers to accompany him. His forcible abduction of the two was stopped by Kanao Tsuyuri, Sumi Nakahara, Kiyo Terauchi, and Tanjiro Kamado, who then proposed to accompany him on his mission instead, alongside his partners Zenitsu Agatsuma and Inosuke Hashibira. Satisfied with three willing Demon Slayers, Tengen began the mission to save his wives and Yoshiwara's people. Upon arriving to Yoshiwara, the trio were amazed by the bustling city and separated from Tengen, with Zenitsu being beckoned by the girls of the district, and Tanjiro and Inosuke in awe of their surroundings, having lived in the mountains their entire lives. They regrouped at a house and were assigned disguises in the hopes the three Demon Slayers could be taken into the three most prominent pleasure houses, as Tengen assigned his wives to. Tanjiro, due to his diligent and hardworking attitude, was taken first and went to the Tokito House, where Suma was assigned. Later, Tengen, Zenitsu, and Inosuke watched as the Oiran of the Tokito House, Koinatsu, travelled with her procession to a new client. Inosuke was then spotted by a chaperone of the Ogimoto House, which held Makio, where he was promptly taken in. Zenitsu is left last, with Tengen assigning him with the Kyogoku House, the same house as Hinatsuru, much to the latter's displeasure.

After the three settled in, they each began their own investigation. Inosuke, upon learning that Makio has not left her room for some time, barged into her quarters to find the place torn and dishevelled. Seeing the windows closed and with no other possible exit, he surmises a demon is in the attic and tries to pursue it. It flees downstairs and Inosuke loses track, with his kimono hampering his acute senses. Meanwhile, Zenitsu uses his sense of hearing and detects a young girl crying in a messy and destroyed room. He attempts to comfort her and ask what has happened, but finds himself confronted by the Oiran of the Kyogoku House, Warabihime.

However, her sudden appearances and inhuman nature startles Zenitsu, believing she may be a demon, and an Upper Rank at that.