Yami is a strong sword, radiates with a powerful aura and drives fear to those who approach it. It is a black sword, wielded currently by Masamune. This sword currently is one of the Twelve Saijo O Wazamono swords in the world.
Yami is a regular katana and its hilt looks as if a normal sword. The katana look is quite useful for users of Battojutsu for the reason that it requires a katana for use, to be able to draw it from the sheath quickly. The blade gives off a somewhat of a glow and shines in the daylight, and even glows in the darkest night despite the katana taking a black color. The material of the blade takes a black color, although it suggests that it were imbued with Haki during the forgery, making it stronger than steel and able to cut through it as if it were nothing, if held by the right user. This sword had been forged with Haki, and had become one of the legendary Saijo O Wazamono swords, reflecting the amount of strength it radiates with the aura felt by all even without Kenbunshoku Haki
Masamune's father had been the first one to bring this sword into the family, he had gained it from his master, and his master had obtained it without Masamune knowing how. This blade had been used unwillingly by Masamune's father, not accepting his ambition and strength it had led to his downfall. His father's defeat had been because of the sword unwilling to fight any further with him, and had led to him being killed on the spot. Masamune had taken this blade, and at first it did not follow him, and was not useable by him despite his many attempts.
Masamune had trained alternatively with a wooden sword and was driven by his ambition, that the sword had sensed every day, as if it itself were a living being. Every day he had tried to wield this blade, and had failed, only to end up getting closer to being able to wield it every day. Masamune had fully mastered this blade when it gave in to his determination, allowing Masamune to wield this sword and the power it brings with it, he still uses it to the present. Masamune and his blade had become completely attune to each other, giving one another their strength allow for a partner-ship like presence between him and the sword.
Author apologizes for bad recoloring work on the blade.