Akikage

Akikage (秋影, Autumn Shadow), often regarded as is a sword whose existence relates more closely to a conceptual armament. It was created by Kazuhide for the express purpose of providing Mukūrō with a tool capable of extended combat against opponents that require a far greater level of power than those that may be dealt with through Nakizura — a mortal blade.

Like all blades of a similar status, Akikage, in its basic design, is capable of dealing great damage with only simple slashes. This can be attributed to the cutting power of the blade, especially given the nature of its creation. However, its true powers lie in the fact that it is capable of absorbing chakra. This chakra absorbing nature of the blade makes it a great asset to Mukūrō, especially given that the blade's properties respond to the nature of the chakra absorbed. While its default state is a katana, by absorbing foreign chakra, the blade adapts to any shape that is best suited for the situation. Of course, all these shapes are offshoots of a katana and thus retain the base definition of a sword. This enables Mukūrō to endlessly adapt to any opponent, overcoming them regardless of the nature of their abilities, making it a sword that could easily be more fearsome than even the famous Seven Ninja Swordsmen of the Mist wield.