No One Knows My Cat Is a Real Monster

Fred wanted a beast worth having out of the summoning ceremony. What he gets in his last year of school is a Shadow Cat at F rank, the bottom of the scale, and while he is standing there his girlfriend Rhea accuses him in front of everyone and ends it with him. The school expels him. He is left with the cat. The God-Tier Beast Master System wakes in him a moment after that. The Shadow Cat is pushed up through a million levels of growth into a god-tier beast that feeds on energy, the Chomper, which kills Citybreaker-class beasts in one strike and holds down Nationbreaker-class ones without much effort. The Void Devourer comes to him as a guardian beast soul. The guild names Rhea the greatest genius in a hundred years, and she has no idea that the boy she threw over has already reached Worldbreaker. Fred is going for godhood. He picks up inheritances of power as he goes, works with some beast masters and against others, and the beast tides keep arriving.