"Long ago in a distant land, Aku, the shapeshifting master of darkness, unleashed an unspeakable evil. But, brave samurai, pure of heart, wielded a magic sword, had stepped forth to oppose the sorcerer of sorrows. Before the final blow was struck, Aku tore open a portal through time and flung him into the future, where his evil is law. After a time, the samurai, having face many challenges and saving many lives, returned to the past and undid the future that was Aku."
Finn: "..... I want that sword."