Seiichirou Kondou, a Japanese accountant in the modern world, tries to save a teenage girl from a magical portal but falls through it with her. It transports them to a kingdom that had summoned the girl to be their Holy Maiden, and Seiichirou receives a job in the royal accounting department. To support his intense work ethic, Seiichirou begins a habit of drinking energizing tonics, not realizing that this could be dangerous to his health. One day, he experiences a tonic overdose, and the knight captain Aresh Indolark uses a healing spell on him. However, this worsens Seiichirou's condition because he lacks a tolerance for magic, and the only treatment is for Aresh and Seiichirou to engage in sexual activity and physical contact.