One evening, master moocher and game programmer Keita Ibuki is making his way home after a bender when he decides to satisfy a craving for ramen at a noodle stand. Instead of slurping the soup, however, he gives his meal to a manic girl who, unknown to Keita, is a Mototsumitama, a guardian of the coexistence equilibrium. When his new acquaintance is attacked, Keita gets caught in the crossfire and loses an arm. Awakening from the shock of his injury, Keita finds himself back in his apartment... with his arm intact! But just whose arm is it?! Asking the strange girl raiding his refrigerator reveals only that Keita's life has become a great deal more complicated.