Along with his step-mother and two step-sisters(step-aunts), the protagonist is summoned into another dimension, where demi-humans are the rulers, and they are to battle “Dead Mell,” monsters that have conquered the world and that can only be killed using weapons made with holy silver.
For this, a family unit is created (a group of 4 people) with them being the leader that employs the holy sword, the guardian that employs the power of the earth to defend, the healer that employs the power of water to cure, and the black mage that employs the power of fire to kill.
The guardian and the mage’s role is to help the swordmaster, who is the only one who can destroy the monsters.
To harness magical forces, one must sacrifice part of oneself for a binding contract with the supernatural world, and the higher the sacrifice, the higher the force. Now they must determine who among the three will forfeit their life to gain strength and who will wield the Holy Sword.