Game Of Familia: Kazoku Senki

The lead character, along with his stepmother and two stepsisters, is summoned to another world ruled by demi-humans. Their mission isn't to battle a demon lord, but rather to combat a swarm of undead monsters dubbed "Dead Mell". The creatures have taken over the world and can only be vanquished by weapons containing holy silver. The group forms a familia, comprising a swordmaster equipped with the holy sword, a guardian who uses the earth's energy to protect, a healer who wields the power of water to mend, and a black mage who manifests the power of fire to incinerate. The role of the guardian, mage, and healer is to support the swordmaster, who is the sole individual capable of slaying the monsters. To use magical abilities, one must offer up a portion of themselves as a sacrifice to forge a contract with spirits. The greater the sacrifice, the greater the power. Now, they must determine which three members will sacrifice part of their bodies to acquire power and who will wield the holy sword.