Warning: The following article contains spoilers for Blue Exorcist.
Some people go to therapy to deal with their inner demons. Others go to anger management classes to solve their turmoil. Still others go on a long vacation to regain their peace in nature. And then there’s always the option to seal your “Demon Heart” inside a supernatural sword, thus managing to keep your destructive side in check, something that works for protagonist Rin Okumura in Blue Exorcist.
To prevent his demonic personality and powers from being unleashed, Blue Exorcist‘s heroic spawn-of-Satan main character has this arrangement set in place, allowing his human side to remain dominant most of the time. That being said, the weapon that contains his heart (the source of his devil powers, in case this wasn’t clear) isn’t fail-safe, and he has the option to decide when and if he wants to unlock his demon energy. So then, what is Rin’s sword called anyway, what can it do, and what is its history in Blue Exorcist?
The sword’s name, powers, and history
In Blue Exorcist, Rin’s sword is known as Kurikara, or The Kouma Sword. It’s a Maken katana, a weapon that’s endowed with demon powers. While most Maken swords are either Possession (swords empowered by a demon’s possession) or Divine Protection (swords empowered by a demonic contract) weapons, with a pact being necessary for the sword to receive its powers, Kurikara is neither of these two types. It essentially acts as a supernatural “chest” of sorts that seals away Blue Exorcist‘s lead’s “Demon Heart,” which he can “unlock” at any time by unsheathing the weapon. He is able to conveniently carry it around in a red sword-bag on his back.
As seen in many of Blue Exorcist‘s battle scenes, parting the sword from its sheath effectively unleashes at least part of Rin’s demon powers as well as a darker personality. His supernatural abilities include superhuman strength, fire manipulation, regeneration, and telepathy. Also, as early as his first transformation in Blue Exorcist‘s second episode, we see that his appearance changes when he draws the katana. In addition to developing red irises, he grows pointy ears, sharper teeth, horns, and a tail, while the weapon becomes enswathed in blue flames.
To top it off, Kurikara isn’t just a container for Rin’s demon side in Blue Exorcist. In fact, it’s revealed that the sword is a “door to anywhere,” with the hilt leading to Gehenna and the scabbard as the door. Together, these can be used to seal demons inside of Gehenna, even after the blue-eyed, black-haired half-demon’s heart is housed inside.
However, despite giving the boy access to at least part of his true abilities, there’s a downside to unsheathing the katana for Rin. In Blue Exorcist, we learn that if the blade is destroyed, he could potentially die when his “Demon Heart” is returned to him (that being said, when the blade ultimately breaks during a climactic fight, he’s able to create a replacement blade out of flame in its place and survives the return of his demon powers).
Through careful training, Blue Exorcist‘s hero is ultimately able to learn to control the powers that his weapon contains, practicing to refine his blue-flame techniques. He even figures out how to use Kurikara when its blade is sealed, and utilizes various demon-sword moves with the special katana.
Blue Exorcist‘s Kurikara was created by Mephisto Pheles, otherwise known as The King of Time or Johann Faust, as well as being the strongest of The Eight Demon Kings and the principal of True Cross Academy. He first gave it to Fukaku, the founder of The Myoo Dharani, who used it to defeat The Impure King (with Kurara, a fire demon, housed inside). After that, it remained in the sect’s possession until Shiro Fujimoto received it from Tatsuma Suguro as payment for eliminating a miasma plague.
Although Shiro had been instructed by Mephisto to steal the katana and slay The Devil’s offspring with it, he ultimately completed neither of these tasks. Instead, he raised Rin and Yukio as his own children, and housed Rin’s “Demon Heart” inside the sword. In Blue Exorcist‘s second episode, it comes into the boy’s possession, where it thus far remains.