Until 20 years ago, Enma was wielded by Kozuki Oden alongside his other sword, Ame no Habakiri. In Oden's hands, both blades became the only weapons known to ever (until the present day) injure Kaidou. After Oden's death, Enma was inherited by his daughter, Kozuki Hiyori, who would later gift the sword to Zoro in exchange for the latter allowing Shusui, a national treasure, to remain in Wano.
On the cover of Volume 96, Enma is seen to be a moderately curved Shobu Zukuri-style katana with a lilac and gold color scheme. Like the Ame no Habakiri, the tsuba is trefoil-shaped, and each lobe is holed in the middle and thickly ridged. The tsuka is lacquered solid lilac (rather than cloth-wrapped), as is the saya. Both are embellished with simple, golden, five-petaled flower motifs on each side. The kashira and kojiri are matching in appearance, being large with trefoil cutouts to match the tsuba; the kojiri possesses an additional accent, which seems to be a wide, knobbed ring above it. Like the Kitetsu swords, Enma also possesses an irregular flame-shaped hamon and black no-hi.
Three pieces of cord are present on the sword: one directly above the kashira (without hanging end), another on the saya a short bit below its mouth with two hanging, tufted ends (serving as the sageo), and yet another cord further below on the saya (again no hanging end). Further, a little bandaging is present on the tsuka for better grip.
In its initial depictions, in the A-ra-shi: Reborn video, its tsuka is black, and its hamon is golden. As seen in the opening "DREAMIN' ON", Enma's anime color scheme is a violet tsuka, as well as a violet sheath.
As a masterpiece of legendary swordsmith Shimotsuki Kozaburo and one of the 21 Great Grade swords, Enma is among the best swords in the world, with Kozuki Hiyori deeming it a worthy replacement for even the legendary Shusui. Tenguyama Hitetsu has described Enma as able to "cut through to the bottom of hell" (paralleling Ame no Habakiri being able to "slice heaven itself").
Enma yields tremendous power and sharpness when fully mastered. In the hands of Oden, it became one of the only weapons known to ever harm the nigh-invulnerable Kaidou, giving him a massive scar. 41 years ago, at 18 years old, Oden used Enma (alongside Ame no Habakiri) to cleanly bisect the giant Mountain God, having hardened it by using Busoshoku Haki. Additionally, Oden was able to use both his swords to clash against Whitebeard wielding his Supreme Grade sword, Murakumogiri.
Enma also has the distinctive trait of drawing out Busoshoku Haki (known as "Ryuo" in Wano) from its wielder in excessive amounts when swung, cutting far more strongly than intended. This makes it extremely difficult to wield, so much that Oden was the only one to have ever tamed Enma. After testing it out for the first time, Zoro accidentally ended up cutting a large cliff section off its base after initially attempting to cut a tree, with Enma not only forced hardening on but emaciating his whole arm.
Hitetsu noted then that a normal swordsman trying to use Enma would be drained of all their Haki and rendered a dry husk, but as demonstrated by Zoro, with sufficient mastery of Haki, one can force the Haki extracted by Enma to flow back from the blade.
Throughout the battle on Onigashima, Kaidou sensed a "Strange Haki" coming from Enma each time Zoro imbues Busoshoku Haki inside of it, causing it to release a black flame-like aura, which he described as bearing Oden's presence, causing him to recognize Enma as one of his swords. If applied onto his techniques, it has allowed him to wound Kaidou, then even gave him another permanent scar.
Anime and Manga differences
In the anime when Zoro accidentally cuts the coastline while trying out Enma, his swing somehow generates fire. This fire is absent in the manga.
Due to its special attributes, no samurai had managed to wield Enma until it was eventually acquired by Kozuki Oden, who managed to master it as part of his Oden Nitoryu. Oden later used Enma to wound one of the Four Emperors, Kaidou, giving him his only scar. After his death, it was entrusted to Hitetsu for safekeeping in order to pass it on as an heirloom onto Oden's daughter, Kozuki Hiyori.
Wano Country Arc
After Hiyori begged Roronoa Zoro to leave his stolen Shusui, an O Wazamono grade sword in its rightful place as a national treasure in Wano though he earned the sword from its previous zombified owner, she offered Enma as an equal replacement. Zoro agreed to Hiyori's proposal to return Shusui for Enma, despite Kawamatsu's initial protest. Upon gaining the sword from Hitetsu, Zoro tried it out and learned of its distinct properties, to which he accepted, and trained during the time before the raid on Onigashima to gain further mastery over Enma. During the Fire Festival, Zoro succeeded in controlling Enma's special trait, becoming the second swordsman after Oden to have mastered Enma.
- Enma is the king of Hell in Japanese-Buddhist myth, the judge of dead souls. He is the Japanese version of Yama, the king of hell found in sects of Buddhism across East Asia; Enma mostly derives from the Chinese-Buddhist Yánluó, who in turn is based on the Hindu (Vedic) god of death, also called Yama.
- Zoro's new ownership of Enma is in accord with his character theme of Buddhist spirituality since many of his sword techniques follow Buddhist terminology/imagery.
- In a flashback, Oden is shown wielding a sword with a different tsuba from either Enma's or Ame no Habakiri's.
- On the cover of Chapter 937, Zoro was seen reading a map featuring a sword and the word "Enma".
- Enma is also the name of the shrine in a forest of Hakumai where Hiyori and Zoro end up.
- Hitetsu believes one reason why Hiyori bequeathed Enma to Zoro is because of his superior strength, skills reminiscent to her father, and his possession of Wado Ichimonji, which like Enma was crafted by Shimotsuki Kozaburo.
- Enma was first animated in the 2020 music video of the boy band Arashi's 2019 song A-ra-shi: Reborn, made with collaboration with Eiichiro Oda, and featured the Straw Hat Pirates partying with the band.
- The panel of Zoro keeping Enma in the manga is extremely similar to that of Zoro keeping Sandai Kitetsu.
- Enma is similar to Luffy's signature straw hat, as they were both once owned by members of the legendary Roger Pirates before being passed along to a member of the Straw Hat Pirates.
- Enma's size is unexplainably inconsistent as it is displayed being fit for both Oden and Zoro in spite of the huge difference of height between them (while Zoro heights 181 cm, Oden heights 382 cm). The same would apply for Ame no Habakiri as it was shown as a regular sized katana when not wielded by Oden.