MTL - Ultimate Assassin System - Chapter 4 The legendary guardian

Lacking a pocket dimension, lacking a power, lacking a thigh to hug onto and the three life advantages (money, power, and looks), he had been cautiously living in the apocalypse for ten years, getting closer to falling inside the zombie’s mouths. But unexpectedly, he had the terrible luck, to be caught in a fight between two gangs and die, it really left people feeling disappointed.

Shaymon, the man who has achieved the apex of dark magic, is framed as being a Demon King and is killed.

Leon is an average high school student who likes to watch anime and read novels.
He's about to cross the street, only to be greeted by a truck and died.
But, he got reincarnated as Uchiha yet dead again because Itachi killed him.
Leon got reincarnated again as the grandson of the recovery girl.
He got kidnaped and tortured by All For One.
After his third death, he got reincarnated as a son of Bibi Dong.
In this fourth life, he wants to change his fate to become the strongest.

Note: Please read the tag before reading.
- English is not my first language, so there would be grammatical mistakes in this story.
- Please give my story a proper review.
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[Beast Mastery][Summoning][Pets][Evolution][Development]Demon, Savage, Nether, Damnation, Mechanism, Soldier, Medicine, Abnormal, Witch, Immortal, Ferocious...This world is a world of monsters, filled with countless diverse “Fond Spirits”.But in this world, humans also wield the power of “occupation classes”. Once awakened, they can have Contract Imprints, allowing them to form contracts with the monsters, creating entirely new bonds.[For Instance]♦F-level Occupation Class “Manicurist”- helps the Fond Spirits trim their claws, making them beautiful, or sharper.♦E-level Occupation Class “Hunter”- marks and chases, closely collaborating with the Fond Spirits, the most classic hunting occupation class.♦C-level Occupation Class “Puppeteer”- manipulates Fond Spirits at crucial moments, making their strikes more precise and powerful.♦B-level Occupation Class “Midwife”- assists pregnant Fond Spirits with health checkups, giving random blessing effects to the newborns.♦B-level Occupation Class “Mechanic”- under the right conditions, modifies the Fond Spirits, turning them into semi-mechanical beings.♦A-level Occupation Class “Dragon Knight”- rides dragon-type Fond Spirits into battle. Man and dragon unite, becoming invincible.♦S-level Occupation Class “Arch Warlock”- intensifies the elemental properties of Contracted Fond Spirits and seals their skills in advance to execute forbidden spells for the second time....♦C-level Occupation Class “Fitness Trainer”...♦D-level Occupation Class “Flame Thief”...♦A-level Occupation Class “Mysterious Merchant”...♦B-level Occupation Class “Gourmet”...♦Special Occupation Class “Brave”......(I already have a completed work of 3 million characters titled “Master of Pets”. “The Rising of the Fond Spirits” is my second work, a Beast Mastery tale with entirely original settings, you're welcome to try it out!)