炭治郎等人結束無限列車的任務之後，在蝴蝶屋過著療養的生活。在這期間，炭治郎為了替煉獄傳話而拜訪煉獄的老家。炭治郎對於已故的杏壽郎被父親・槙壽郎侮辱感到憤怒，但槙壽郎在看到炭治郎的耳飾之後，突然變得認真了起來。究竟炭治郎會在煉獄家得知什麼事情呢？

炭治郎、禰豆子、善逸、伊之助跟著宇髓前往執行任務。他們抵達的地方是夜晚燈火通明的街道・遊郭——雖然宇髓的三位老婆已經潛入蒐集鬼的情報，定期聯絡卻中斷了。炭治郎等人為了打聽情報，只好變裝之後到各個店家進行潛入任務……

遇到上弦之陸・墮姬的善逸雖然察覺到她就是鬼，同時墮姬也注意到善逸是鬼殺隊的成員。於是，在那之後善逸便下落不明了。為了定期聯絡集合的炭治郎與伊之助，從宇髓口中得知了這個情報，並且被告誡要離開遊郭...

善逸下落不明後，炭治郎與伊之助被宇髓告誡要離開遊郭，但是兩人仍決意要救出善逸等人。當天晚上，炭治郎察覺到鬼的氣息，循著氣味抵達的地方，撞見鯉夏花魁被墮姬的腰帶吞噬的模樣。在宇髓等人都不在的情況，炭治郎將要獨自一人面對上弦之陸。

與墮姬持續進行激烈的戰鬥時，炭治郎連續使出對身體負擔很大的「火之神神樂」。與此同時，抵達腰帶鬼巢穴的伊之助，救出了被腰帶囚禁的人們。被救出的牧緒、須磨、善逸加入戰局，突然，巢穴的天花板被破壞了――宇髓便現身揮舞刀刃。

炭治郎對於藐視人命的墮姬感到憤怒。雖然將墮姬逼到如此地步，炭治郎的身體早已超過極限。在炭治郎倒地、再次陷入危機的時候，禰豆子趕到他身邊。禰豆子挺身對抗墮姬、進行猛烈戰鬥的同時，外表也變得越來越接近鬼的身姿……。

After Nezuko attempts to attack innocent bystanders as her demon form advances, Tanjiro is finally able to make her fall asleep by singing a lullaby. Meanwhile, another demon emerges out of Daki's body after being beheaded by Uzui - Gyutaro, Daki's older brother and the other form of Upper Six. Uzui must now face both demons, Daki and Gyutaro.

Tanjiro, Zenitsu and Inosuke have joined Uzui in battle. While Zenitsu and Inosuke take on Daki, Tanjiro and Uzui deal with Gyutaro; however, they struggle as the demons have the upper hand with their coordinated attacks. But thanks to Hinatsuru's help and some teamwork from Uzui, Tanjiro's blade finds its way towards Gyutaro's neck...

Tanjiro and Uzui have been separated by Gyutaro’s Blood Demon Art. As Tanjiro joins the struggling Zenitsu and Inosuke, they manage to decapitate Daki at last thanks to their coordinated barrage of sword strikes. However, when Inosuke tries to run off with Daki’s head, he gets pierced by Gyutaro’s scythe. Uzui has also collapsed, leaving Tanjiro and the others with their backs to the wall.

Uzui deflects all of Gyutaro's Blood Demon Art attacks, and despite getting pierced in the jaw, Tanjiro is able to slice off Gyutaro's head. Though wounded from head to toe, Zenitsu and Inosuke also behead Daki, and they succeed in decapitating both demons at the same time. Just when it seems as though they've defeated the Upper Six demons after a fierce struggle, Gyutaro unleashes his Blood Demon Art...