A mistake by a team of researchers opened the gate to the realm of Entomorphia, releasing giant bugs called Entomorphs. The sheer number of Entomorphs and their immunity to metallic weapons pushed humanity to the brink of extinction. But humanity was saved by another alien species called spirits. These spirits were living among humans, posing as different animals. Seeing the Entomorphs massacring humans, they extended their arms to them. Making contracts with them, humans used their spirit powers to fight against the Entomorphs. One day the MC, Ray Foster comes across a cat with bruises all over her body. He decides to take her home and take care of her. What he didn't realize was that the cat was a spirit. As thanks for taking care of her, the cat makes a contract with Ray, turning him into a spirited. Thus the journey of the world's strongest Jaeger begins.