A Psychiatric Patient's End-of-the-World Game

(Apocalypse, gaming, cozy family moments, goofy humor, no saintly protagonist, dark sides of human nature, mostly sweet, no excessive angst)

The apocalypse arrives, and everyone around the world under the age of 15 or over the age of 50 dies overnight. The humans who remain can all level up by killing monsters...

Some people say the world has become a madhouse, where the only choices are to kill or survive. But in a world like this, who among the living isn't a little crazy?