===Origin===
Sheen's Japanese name, Masamune, refers to Gorou Nyuudo Masamune, a swordsmith of the late Kamakura period, acclaimed as the greatest in Japan's history and mentor to many great swordsmiths. He crafted extraordinarily beautiful blades of high quality, in spite of how scarcely available pure steel was at the time: in particular he had perfected the art of <i>nie</i>, a method of embedding hard steel crystals in the forged blade, creating a finish that resembled a starry night sky. Contrasting with the legends around <a rel="nofollow" class="external text" href="https://en.wikipedia.org/wiki/Muramasa">Muramasa Senji's blades (see Snee#Trivia), Masamune's swords were said to have a pious, even gentle soul to them, and would only cut what their master willed them to without taking lives indiscriminately.
One legend claims the two competed to see who could craft the finest katana: when both their swords were hung over a river facing the current, Muramasa's blade sliced all fish and dead leaves that floated through it, while they glided gently around Masamune's. The judge deemed Muramasa's sword technically perfect, but cursed and bloodthirsty, while Masamune's was a true weapon of justice, and for that reason he was declared the winner.