神獣は亀ですが、なにか?

In a monster-ravaged world, beast taming is dead. To save his dying sister, a poor boy awakens the ultimate system and contracts his pet turtle! Surprise—it has a god-tier bloodline that evolves by devouring enemies! Taming other mythical beasts, he crushes a millennial conspiracy. Watch this underdog rise to become the supreme Beastmaster!