My Dog Accidentally Ate an S-Class Monster

Transmigrated before the monster apocalypse, Xavier Lynn only wants to protect his younger brother and avoid past betrayals. He takes in a stray "dog" named Darkwind, only to awaken the Absolute Contract, a power that lets him forcibly tame S-class monsters. But when Darkwind swallows an A-class monster and his brother Jack extends SS-class tentacles from a water vat, Xavier realizes his "helpless" brother is terrifyingly strong.Meanwhile, the ex-girlfriend who got him killed and a corrupt military officer now have their greedy eyes set on his home.