You’re a beast tamer who was expelled from the hero Arios' party who consider you too weak because you only has the ability to form contracts with animals. While looking for work, you rescued Kanade, a member of the cat spirit tribe who becomes your companion. By forming a contract with a member from one of the strongest races known as an "ultimate species", you obtains some of her powers, becoming much stronger. The two then begin their journey together, with you befriending and taming other girls from different races who become powerful companions while obtaining new abilities with each new contract formed, your group eventually becoming far more powerful than Arios and his party. Overcome with anger and frustration, Arios begins loathing you, neglecting your duties as a hero and focusing on revenge against him and his friends instead.