Rein Shroud is a beast tamer who uses animals for scouting and hauling, and that earns him a place in the party of the hero Arios Orlando. After six months, the vile, manipulative hero throws him out as useless because his class cannot fight. Rein does not give up on adventuring. He takes on simple quests and soon meets Kanade, a cat spirit belonging to the ultimate species, rare beings of enormous strength and magic that many humans covet. Rein proves to be no ordinary beast tamer when he forms a contract with her. With Kanade at his side, he climbs the adventurer ranks and encounters more of the ultimate species along the way, in a fantasy adventure about the talent his old party failed to see.