The story begins with Ryosuke Tanaka, a 35-year-old salaryman, tragically dying in a motorcycle accident. He is reborn as Shunsuke, the third son of a farming family in an unfamiliar world. Three years pass, and Shunsuke, retaining his adult consciousness, begins to understand his new reality. His family consists of his father, Tamasuke, his mother, Shizue, and his two older brothers, Ryunosuke (11) and Toranosuke (10). He discovers that this world, while similar to Japan, possesses magic. His mother, Shizue, demonstrates "Chakka," a fire-starting spell, revealing the existence of "life magic." Shunsuke, having read fantasy novels in his past life, is thrilled and begins practicing magic himself. He learns that magic is fueled by "mana" and that overuse can lead to exhaustion. He also discovers that his mana capacity increases with practice.
Life in their village is simple and lacks entertainment, leading Shunsuke to dedicate his time to mana manipulation. He befriends Kyoko, the village chief's granddaughter, who is the same age. Kyoko, bored with traditional girls' games, invites Shunsuke to her home, where he discovers books. He finds a book detailing magic and learns about "Hyuga no Kuni" (Land of Sunlight), a nation renowned for its "Matojutsu" (Magic Combat Technique). He also learns about the world's political landscape, divided into three continents: Demon, Beastman, and Human.
At age seven, Shunsuke has become proficient in Matojutsu and a new skill: "Appraisal," which allows him to identify the abilities of monsters. He secretly ventures into the nearby forest, which is home to low-level monsters like goblins and slimes. While hunting, he encounters two foreigners, Pedro and Nicolas, who have golden hair, marking them as outsiders. They are lost and arguing when they are attacked by an Ogre and a horde of goblins. Shunsuke intervenes, swiftly defeating the goblins with his wooden sword and Matojutsu.
Pedro and Nicolas are astonished by Shunsuke's combat prowess. They learn that Shunsuke is from Kanrin Village and offer to guide them. During their journey, Shunsuke asks them to keep his forest excursions a secret from his parents. Upon arriving at the village, Pedro and Nicolas are welcomed, and it's revealed that Shunsuke's father is the village's best swordsman.
During their ten-day stay, Pedro and Nicolas reveal they are searching for a rare variant of the "One-Horned Rabbit," also known as the "Rabbit of Fortune," which is valuable for its tail used in crafting "Magic Bags." Shunsuke and Kyoko assist them in their search. Shunsuke also teaches them about mana manipulation and Matojutsu, a skill highly valued in their adventurer ranks. The foreigners, who are B-rank adventurers aiming for A-rank, are impressed by Shunsuke's abilities.
On their final day, despite their efforts, they fail to find the "Rabbit of Fortune." However, Shunsuke, using a newly developed detection technique based on Matojutsu, manages to find a yellow-tailed rabbit. The foreigners are overjoyed, and as they prepare to leave, they express their gratitude for the experience and Shunsuke's help.
