Its Name is Enma! Oden's Great Swords!

Kawamatsu relates the tale of Gyukimaru, revealing the thief to be a fox called Onimaru. Rather than let Zoro reclaim the sacred Shusui, Hiyori proposes a trade and offers him Oden's own weapon, Enma, placing the legendary blade in his grip.

Chasing Gyukimaru, Zoro loses him through a derelict doorway. Hiyori and Kawamatsu set off together but are swarmed by another wave of bandits, whom Kawamatsu drives back while recounting what happened after Hiyori vanished. Thirteen years before, he had traveled to Ringo, a land whose daimyo had been Shimotsuki Ushimaru, kept company by his fox Onimaru, until Orochi's coup left Ushimaru slain and Ringo fallen. There Kawamatsu came upon a vast burial ground of Eternal Graves, where the cold preserved the dead inside caskets, each marked by a sword said to hold its owner's soul. Grave robbers coveted those blades, but Onimaru kept watch over the site.

Wary of Kawamatsu at first, Onimaru gradually warmed to him, then bristled anew on seeing him pull swords from the graves. Once Kawamatsu explained the blades were meant for the raid, and that the samurai spirits within would aid their wielders, the fox relented and helped him collect more. The two built a hideout, lifted food from the capital, and beat off robbers, until Kawamatsu was caught in a trap while stealing tofu and dragged to the Udon mine. In the present, he returns to where Gyukimaru disappeared and finds the sword cache, telling Kin'emon the army now has its weapons. Gyukimaru, it turns out, was Onimaru in human shape through the Hito Hito no Mi, Model: Onyudo, and having arranged the blades during Kawamatsu's absence, he reverts to a fox and departs. When Zoro reaches for Shusui, Hiyori stops him and holds out Enma instead, the blade Oden once carried and the only sword ever to wound Kaidou.

Added material shows Zoro watching Gyukimaru open the cache, Kawamatsu cutting down more Beasts Pirates, a flashback beat of him close to ending his own life before hearing Onimaru fight, and his net-trap arrest by Orochi's enforcers. Page One, Sasaki, and Who's Who appear in silhouette, though Who's Who's flashback presence is non-canon, since Chapter 1017 establishes he was in CP9 thirteen years prior. The scrap with Bingo, Bongo, and Bungo is drawn out. Shimotsuki Ushimaru debuts, and the episode runs in the Wano Country arc.