Linus's soul has been transferred into the body of an 18-year-old boy with the same name and looks, but this isn't earth anymore. He has arrived at a new planet where vicious beasts capable of flattening mountains reside outside the human cities. Humans on the other hand have survived by contracting those beasts and becoming pet trainers after awakening and cultivating their contract space. Linus is determined to become a mythical pet trainer with a mythical beast under his control, but will he succeed as an orphan who doesn't even have enough money for the lowest iron rank pet?