Fantasy

[Tower Defense + Infinite + Survival + Harem (Gathering Wives) + Upgrade]
    After regaining consciousness, everyone discovered that they had been taken to a strange building, forced into participation in an infinite game.
    This world was shrouded in mist, monsters lurked everywhere, and before those horrifying creatures, humanity was nothing more than insignificant ants. The only safe place was their personal room, and the only thing protecting them from the monsters outside was the door.
    Rover was brought into this world as well, but he was fortunate enough to obtain an SSS rank Class: Omni Mechanic. As long as he used [Relax], he could gain Omni Points, allowing him to upgrade anything.
    His harem not only helped defend his room against the monsters but also generated Omni Points for him.
    From [Rotted Wooden Door], he upgraded it into [Immortal Divine Gate]
    From [Wooden Bolt Turret], upgraded into [Radiant Turret]
    From [Zombie Virus], upgraded into [Awakening Serum]
    From [Normal Zombie], upgraded into [Hell Lord]
    His harem was upgraded as well, gaining strength that everyone craved.
    In a world overflowing with despair and agony, Rover was somehow living happily with his harem, as if enjoying a luxurious resort.