Muramasa

Muramasa was an expert swordsmith in Japan.

Biography
Muramasa was apprenticed to Masasmune. He was believed to be able craft a sword just as fine as any his master made, but his dark personality reflected the nature of the weapon and was cursed. The design could achieve sentience of their own and would drive their wielder to bloodthirsty deeds. The sword would lead the wielder to murder and seppuku in spite of any glory that could be achieved in battle.

Personality and traits
Masamune was described as "dark-natured".

Behind the scenes
While Rising Sun's Muramasa is based on legend, it is generally considered the real Muramasa and Masamune lived in seperate time periods and as such, there was no possible apprenticeship.