The story follows Ginta Toramizu, a boy who always dreamed of a fantasy world, but now has actually been transported to one - MÄR Heaven. Here, his physical weakness is replaced with physical strength. Ginta quickly meets the mysterious witch Dorothy, who introduces him to the powerful ÄRMs; artifacts that can possess the power to transform into weapons, summon monsters, or other abilities. Ginta obtains a special ÄRM call Babbo (バッボ). Babbo is unique: not only is he a weapon ÄRM, but he is also alive and can therefore talk, drink, and move of his own accord. Babbo was once the weapon of an infamous Knight named Phantom, the leader of the Chess Pieces who have returned to conquer MÄR Heaven.