Ken to Mahou no Zeikin Taisaku (Light Novel)

A world ruled by a certain “strange law”. In a time when hero and demon lord cooperate, a beautiful angel appeared. That angel told the hero this. [You have obtained half of the world. A tax will be imposed related to this donation.] In short, that “strange law” is paying taxes to the god. The hero, who is frightened by a enormous donation tax caused by immense fortune that is “half of the world”, chooses a way to escape from the taxes. And that is to fake a marriage with a demon lord and to rely only on one girl. That girl’s occupation is the only one that can oppose tax angel, and with this tax accountant survivor.