Kumamoto Blade is a mysterious weapon forged by a blacksmith during WWII. The blade was built under the corporation with the blacksmith-Hephaestus and the optics expert - Evelyn Hoover worked at the Ferderal Secret Service who studies physics with her whole life. Evelyn spent her whole life at inventing a weapon that can penetrate lights, the photons actually, because lights are form by photons. Evelyn had the theories and experiment, but she does not have the smithing skill. At the middle of WWII, the weapon was made and use in the battle, which causes a serial of unknown death.
The Kumamoto Blade can cut through all the visible light, which makes the person behind the blade invisible. Whoever holds the blade will become visible and untraceable, the blade reflects the light within the area, so no one can see, just like the cloaks of invisibility in Harry Potter. Any fighter and assassin wants the blade to death.
The blade called Kumamoto Blade is because the last known holder after WWII, is a Japanese Samurai whose name is Kumamoto. After that, no one knows where the blade has gone to.