It is said that to test the sharpness of the blade, forgers would stab the sword into the middle of the river and observe whether the blade could cut a leaf that floats with the current. But for weapons forged by Muramasa, the leaf that parts will be held on by a mysterious force. This is due to the fact that Muramasa uses the forging technique he learned from his master Julian. Which incorporated the ability to communicate with the sword. He is able to understand what each blade is feeling. This means that every weapon forged by Muramasa shares a portion of his soul.
Four Great Demon Blades were created using various Shaman techniques (actual shaman techniques not Shaman abilities) to fuse actual souls into the blades. Although the weapons possess unimaginable power if you can’t use the power, then it’s no different then a piece of trash. There is a legend that says when a Muramasa Blade has to willingly yield to its master. The sword will take control of its master. If a Muramasa Demon Blade is used by a weakling the blade will control that person and literally destroy its master. Moreover most of the owners of the Demon Blades died a gruesome death. It is as if the Demon Blades look for an owner who is able to feed it with more blood. Though very powerful weapons if you don’t use them carefully you might be engulfed by the weapon instead. The Demon Blades continuously absorbs the powers, energies, memories, knowledge, talents, personality and physical abilities (whether superhuman or not) of its wielder. They are not limited to absorbing superhuman abilities. They also absorb the strength, agility, and reflexes the wielder. Their mind remains clear but their reactions gradually get slower. The Blades absorbs the total psyche of a person, and the 'echoes' of their personalities remain buried in them. But if there’s anyone who is able to defeat their Blade, by possessing an extraordinary level of power that they are able to resist it by using their strength to completely overwhelm the blade, it will yield and the wielder becomes the blades new master. Their fatigue miraculously vanishes and their body becomes filled with energy. This is a constant battle between man and machine for example Onime-no-Kyo was able to easily subdue Tenro when he first got it. It wasn’t until after he mastered the full Mumyou Jinpuu Ryu that he started to go through problems. When Tenro realized he wasn’t able to use the art to its fullest potential it tried to take control of him.
TenrouThe Tenrô which translates to "Heavenly Wolf" is a Nodachi. It was named Tenro because its brightness is just like the real lupus constellation in the sky. Tenro is one of that the swordsmith Muramasa forged. Its curve and cut are things of beauty. It is approximately five shaku (equivalent to five feet) long and it cannot be broken, cracked, bent, or dulled. It has no problem cutting through steel weapons or solid iron. Many warriors have strived to obtain the sword, but have failed because of its evil nature. It appears that the human blood that Tenrou craves for amounts to as many as ten to a hundred thousand people. Inside Tenrou is the spirit of the First Aka No Ou, Demon Eyes Kyo's direct ancestor, who was absorbed into the spirit of Tenrou.
The Shibien blade was forged to complement the Tenro and legend says it was wielded by the legendary Sasuke Sarutobi. However it is exceptionally bloodthirsty and violent it's previous owner was able to control it freely and because it absorbed so much blood, it turned black. Its creator, Muramasa, had to have it bound in chains to prevent it from turning on anyone.
Hokuraku ShimonThe Hokurakushimon is a demon spear forged by the swordsmith muramasa. Its sharpness is peerless. The demonic spear was regarded as a guardian to the Tokugawa Clan in the past and was carefully kept. Considered a treasure, it has the tendency to absorb the life of the wearer, making it both feared and revered by the clan. The death of Jirozaburo Kiyoyasu and the wounds Hirotada Tokugawa and his son Ieyasu received any unfortunate event that happened to the Tokugawas are related to the demonic Muramasa blades. Those who opposed them thought the blade hated the Tokugawa, many people also thought that they have been cursed. But only the ‘Hokurakushimon is different from the other Muramasas. It requires the Tokugawa’s dark blood as a price to unleash its full terrifying fury. The blade was sealed deep within the Tokugawa storehouse.
PurposeThe Demon Blades were created in a set of four and are only able to unlock their true power together. They were meant to protect and also defeat the one man given the title of the Crimson King. Their true purpose is to be a set of keys that can open the door that only he who is called the Crimson King can enter, behind which sleeps the greatest secret of the Mibu Clan.
LegendLegend says that before his death Muramasa created one last blade. This blade was a kodachi that he put his Nei into. In the last volume it was used by Tokito (in combination with other Muramasa) to open the door in which stay the greatest Mibu secret.
- Unlike in the manga, there are five True Muramasa in the anime instead of four.
- The Hokuto Shichisei which was a True Muramasa in the manga is not shown in the anime and is replaced by two other weapons, the Hajyo and the Tengoku.