The story begins with Tomoru Hiiragi, a three-year-old boy, suddenly realizing he possesses the memories of a deceased fifty-year-old man from another world. This past life was one of failure, marked by unemployment and a generally unproductive existence, ending with his death after squandering his inheritance. Tomoru finds this reincarnation baffling, wishing for a more fortunate past life's memories. He initially suspects a typical reincarnation trope involving divine intervention and special abilities, but finds no immediate evidence of any "cheat" powers.
However, a status screen appears before him, displaying his attributes: Level 1, with all stats at 30/100, and various skill levels, including General Knowledge (Level 9), Japanese Knowledge (Level 8), Exercise (Level 4), Computer Operation (Level 15), and Basic Magic (Level 1). He lacks a comparison for these stats but deduces they are likely within a child's range. Tomoru is born into a minor lord's family in a border region, a position that, while sounding respectable, is essentially the leader of a small, struggling settlement. The territory is plagued by monster incursions, which damage agriculture and harm the populace, necessitating a large military presence that strains the already dire finances. Despite selling monster "cores," the territory remains on the brink of collapse.
Despite his limitations as a three-year-old, Tomoru decides to take action. He requests training from his father, Baron Hiiragi, expressing a desire to become strong enough to defeat monsters. His father, initially surprised, accepts Tomoru's request, believing it to be a child's fascination with soldiers. Tomoru begins rigorous training, starting with basic falling techniques and then progressing to wooden sword forms. He learns the importance of precise movements and body control, enduring harsh practice sessions with the soldiers. His dedication impresses them, and he gradually gains their acceptance.
Simultaneously, Tomoru dedicates himself to learning. He reads books, finding the Japanese language and script in this world to be a convenient advantage. His literacy is discovered by his butler, who reports it to his father. This leads to a plan to hire a teacher, but the family's financial woes prevent it. Instead, Tomoru begins attending a local shrine, which functions as a school, teaching basic literacy and arithmetic to village children. Due to his existing reading and comprehension skills, Tomoru receives special, individualized instruction from the priest, who recognizes his exceptional talent. His days become a demanding schedule of physical training and academic study.
A year later, Tomoru, now four, checks his status screen. His individual skills have leveled up significantly through his training and studies, including Exercise, Swordsmanship, and basic Magic. He discovers that "General Level" is a separate, much harder-to-raise stat that indicates overall power. He learns that defeating monsters is the most effective way to gain experience for this level. Driven by the need to protect himself from further bullying by Takeji, the son of a local village headman, and to improve his own capabilities, Tomoru decides to venture out and hunt monsters. He gathers rudimentary weapons and armor, preparing for his first solo monster hunt.
His first encounter is with a giant grasshopper-like monster. Using his basic magic, he blinds the creature with a flash of light, then swiftly dispatches it with his hatchet, severing its wings and legs. He harvests its core, which he learns can be used to supplement his magic's MP consumption. He successfully defeats five monsters that day, efficiently using his magic and weapons. The experience reinforces the difficulty of combat but also the effectiveness of his training and the potential of monster cores. He realizes the need to become stronger to handle future threats, both from monsters and from individuals like Takeji.
