A young贵族 named Alto, the third son of a rural noble family, holds territory that includes the ruins of a demon lord‘s castle that was destroyed long ago. On his tenth birthday, Alto receives the Shepherd job, a vocation widely considered weak, difficult to level up, and unsuited for combat. One day, while cultivating the land within the abandoned castle, he discovers a small, injured dog and decides to rescue it. Unbeknownst to Alto, this seemingly ordinary puppy is actually a legendary magical beast.

From the moment he rescues the dog, Alto‘s Shepherd level begins to increase at an explosive rate, transforming him into an extraordinarily powerful individual far beyond common sense. The story follows the hidden strongest Shepherd and his legendary牧羊犬 (herding dog) as they embark on an adventure described as a reclamation gourmet fantasy.

The narrative is set in a fantasy world where the remnants of a bygone demon lord‘s castle serve as Alto’s territory. The initial arc focuses on the development of the castle ruins and the rapid growth of Alto‘s abilities after he unknowingly partners with the magical beast. In the next major arc, Alto obtains the seed of a miracle fruit called the Elf Tomato, which is said to take ten years to grow. By continuously using his Shepherd powers, he cultivates the fruit in just two weeks and succeeds in harvesting it. While attempting to sell the tomatoes in town, he encounters an beautiful elf named Duerranta, who is searching for someone capable of saving her village from the brink of death due to starvation. Alto then decides to travel to the elf village to help them.

The third arc reveals that the cause of the elves‘ plight is a curse on their land. The entity behind this curse is identified as the Exterminator, a biological weapon originally created by the former demon king to destroy all races. Having lifted the curse, Alto becomes the target of the Exterminator itself, which attacks the elf village. As the elves‘ magic proves ineffective against this foe, Alto stands up to confront the ancient weapon in a decisive battle.