The hero's party included Beast Tamer Rein, who uses animals. However, because he couldn't do anything else, he couldn't keep up in battle. "You only know how to play with animals; you're fired." Rein is kicked out of the party and now roams the countryside as an adventurer. On his journey, he meets a girl from the strongest species, the cat tribe. Meanwhile, the hero's party is still unaware that their previous success was entirely due to Rein... This is the story of a beast tamer who can no longer be restrained and his fateful encounter with a valuable companion.