My tamed beasts can't be demons.

Taming beasts, but the spirit pet is just a blade of grass.
[Ding! Congratulations, host, you have awakened the Savior System.]
Our ultimate goal is to nip the beast tamer Zhou Lu in the bud and save the world.
Zhou Lu: "???"
The spirit beasts he has raised will become world-destroying demons, and all living beings will wail beneath their vines. Please do everything in your power to stop him.
Zhou Lu looked at the small grass that was fighting with the bees.
Weak, pitiful, and helpless.
You call this a demon god?
This book is also known as "Taming Beasts Begins with Grass".