Though he had not thought much of it before, Zoro’s memories in the Shimotsuki Village will assist him in understanding what it means to control Enma, one of the 21 Great Grade swords.

Zoro obtained Enma by exchanging Shusui, a national treasure, in Wano Country. Zoro controlled Enma by understanding the sword's purpose and surpassing his limitations. Enma tested Zoro's Haki and ...

which he gave the name of the king of hell. Back in the present, Zoro realizes that the old man was Shimotsuki Kozaburo, the swordsmith who made Enma. Zoro remembers what Ipponmatsu told him years ...

Zoro obtains Enma from Hiyori in chapter #953 in exchange ... The manga eventually gave way to the anime series, with the two being some of history's longest-running anime and manga series.