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. The catch: the upgrades that matter can only be unlocked by specific elemental affinities, so Jax cannot build alone. He starts with Elena Whitmore, the haughty S-Rank Ice heiress abandoned by her own guards. Jax offers her a contract, not rescue, and the arrogant Ice Queen finds her pride melting into fierce devotion. As the fortress grows, he draws in Nyx, the silent Shadow assassin; Dr. Aris, the gentle healer freed from slavers; and Lyra, the feral Beast Tamer. Together they become a lethal, jealous, perfectly united family, and Jax becomes a multi-elemental god. Their rise draws enemies: slaver factions, a world-ending Beast Tide, the coward who abandoned Elena, and finally Warlord Vance, a rival sovereign with a mind-control system who tries to turn Jax's women against him. The Sovereign Bond makes them immune, and Jax's harem destroys Vance's army in a face-slap the wasteland will never forget. By the end, the bunker has become a floating citadel, and the man once left to die stands above a ruined world as its king.”