Seiju no Kuni no Kinjutsukai  

Forbidden Spell Master of the Holy Tree, 聖樹の国の禁呪使い

Sagara Kurohiko, despite failing in his job search and being a shut-in, went on a mountain during a typhoon where he was struck by lightning and died. However, he miraculously survived and found himself in an unfamiliar land with a sacred tree. His physical appearance reverted to his teenage years when he arrived at the academy near the tree. Suspected of being a spy from another country, Kurohiko was brought before the headmaster. An accident occurred on the way, causing the headmaster's wrath. Before Kurohiko could be blasted by magic, he discovered an ancient parchment containing an incantation for "Forbidden Art," an extremely powerful spell from legend. No one had been able to decipher its contents, making Kurohiko the only current Forbidden Spellcaster. The headmaster offered him a place at the academy.