Doomsday: My Fortress levels up when I bond with heroines

On the night the Blood Moon rises, eighty percent of humanity turns into mindless Abyssals. Jax Calloway spent his first life protecting the survivors who then barred the gate and let him die.

He wakes three days before the apocalypse with the Sovereign Bond System. Through mutual, consensual Origin Bonds with Awakened women, Jax copies half of each woman's power, permanently raises his stats, and earns Sanctuary Points to upgrade his bunker into a fortress. Each heroine is lifted a full rank, made immune to Aether corruption, and given a place in his sanctuary.