Twenty years ago, Astaria waged war on the Kim-un-kur, and was in need of weapons. Harden, an Astarian blacksmith who at the time burned with patriotism, put his heart into the creation of the swords.
Wishing to see his masterpieces in action, he headed to the battlefield himself. During this visit, he watched soldiers use his weapons to hunt a +Anima, Margaret; Harden jumped to her defense. Soon after, Harden stopped forging swords in favor of household tools, and the Guardian Hearts were discontinued.