A Sword from Over 300 Years Ago

Nezuko's increasingly powerful regeneration and Blood Demon Art overwhelms Daki, but she accidentally injures a bystander and her demonic bloodlust overwhelms her senses; she almost attacks them before Tanjiro intervenes. Tengen arrives and beheads Daki, doubtful she is an Upper Rank. However, she does not die, and instead, her brother Gyutaro emerges from within her body. Gyutaro, the true Upper Six, heals Daki and battles Tengen with his sickles and Blood Demon Art. Tengen is injured and struggles to defend himself, realizing that Daki cannot die whilst Gyutaro is alive. Tanjiro calms Nezuko down, just as Zenitsu and Inosuke arrive.