[Beast Taming + Gu Insects + Assassin Type + No Female Lead + Decisive Killing + Cannot Transform + Cthulhu + Lone Wolf + Numerous Trump Cards...]

(No system, but it has cheat codes!)

A bizarre invasion has occurred, with ten evil kings emerging, plunging the continent into peril!

Chen Fei, still a freshman in college, obtained the Killing Codex, which allows him to quickly improve the strength, aptitude, and skill proficiency of monsters simply by killing.

Restriction: Only Assassin-type monsters can be contracted.

(The "Assassin" attribute is not a class!)

[The Myriad Poison Gu: Can use a variety of toxins to unleash a Zerg catastrophe!]

【The Ghostly Fox: Possesses three magic systems: soul, illusion, and dreams; kills without a trace.】

[Hidden Void Skeleton King: A combination of necromancy and spatial manipulation, allowing for assassinations with unparalleled freedom of movement!]

[...]

Classmates and friends: "No way, we haven't even graduated yet, and you can already beat up the Evil King?"

"No, we haven't even graduated yet, and you've already ascended to heaven?"

...

This book is also known as: My Pet Beasts Are All Natural Disasters!

Beast Taming: Starting with a Gu Poison and a Cheat Code