Sagara Kurohiko, who failed to find a job and had been living as a recluse after graduating from university, found himself enveloped in a blinding light in the mountains during a typhoon, leading to his unconsciousness. When he awoke, he found himself in an unfamiliar land, a country he had never seen or heard of, where the sacred great tree was worshipped. It seemed he had been transported to another world, and to his surprise, he had been rejuvenated to his mid-teens. Kurohiko, for some reason, could easily read the forbidden spells from a spellbook that no one had been able to read for a long time. This led to his forced enrollment in a school that trains 'Holy Tree Knights' managed by the country. As the only 'Forbidden Spell User' in the school, Kurohiko's new life began. *Currently, the book series is available in volumes 1-9. The web version and the book series have some differences in content.