Kaan's Sealed Soul is obtained by killing the Ruin Kan found in Akma Cave in Einhoren.
The Ring normally drops when he is killed. The ring is considered to be a Healer or Mage class item. Since the Sealed Soul Ring is a blue named item, it cannot be traded in-game. It can only be traded through the exchange market. It is highly recommended any party's killing the Ruin Kan to set the party's distribution to "Free" and have any healers or mages obtain the item.