Merlin Wolford was formerly considered as a national hero in the kingdom of Earlshide, lauded for both his strength and achievements. He prefers a tranquil life, so he retreats deep into the rural forests, devoting his time to rearing an orphan he rescued. This orphan is Shin, a regular salaryman in modern-day Japan who was reborn into Merlin's realm while still remembering his previous life. As the years pass, Shin demonstrates unrivaled aptitude in both magic casting and martial arts, much to Merlin's delight. However, by his 15th birthday, it is clear that Shin has only grown his combat abilities and nothing else, leaving him with obvious social awkwardness, a lack of common sense, and a mediocre sense of responsibility.