Taking a Long Nap in the Middle of a Zombie Horde

The protagonist is pulled by the Apocalypse System into a world crawling with zombies.

The System orders him to survive there for 50 years.

If he makes it through all 50 years, he can return to his original world with everything he has collected there.

Since the previous 99 chosen candidates all failed to last 50 years, he unlocks three innate abilities from the start and is also allowed to choose how he wants to grow stronger.

He can decide for himself how to get stronger, and the System offers three options:

Get stronger by sleeping, get stronger by eating, or get stronger by fighting monsters.

As a 24/7 overworked office drone, the protagonist figures that since the System chose him, he might as well choose to get stronger by sleeping. Now that he’s in this world, he doesn’t want to be a wage slave anymore, and sleep seems like the best option.

But that choice ends up giving him an apocalypse life that’s even more exhausting than working 24/7.