Apocalypse: My Cat Ate the System!

The apocalypse arrived. Everyone else awakened supernatural powers, but my orange cat swallowed my leveling System in one bite.

[Ding! Host binding failed. System is being... digested???]

From then on, everything went sideways. Other people got gear drops from monsters; I got cat food drops for my cat. Other people leveled up and allocated stat points; my cat ate experience points and started evolving: partial steel hardening, rift claws, emotion sensing... The stronger my cat gets, the stronger I get, because our shared buff is the "passive aura of a cat owner."

One person and one cat, taming the System in reverse and carving out a "cat owner's road to the top" in an apocalypse where everyone is caught up in the rat race. The System went mad, the enemies were dumbfounded, and only the cat got fat.

No CP. The heroine is tough and doesn't talk much. Her feline master handles the comedy and firepower. The whole point is "one person and one cat ruling the roost."