Ken to Mahou no Zeikin Taisaku @comic

A world dominated by a certain "strange law". When the hero and the demon king held hands, an angel with a beautiful face appeared. The angel tells a word to the hero. "You got half the world. There is a tax on the gift." So the "strange law" was the "tax" to God! The method taken by a brave man who was impatient with the extremely high gift tax on the huge assets of "half of the world" to escape tax payment. It was a fake marriage with the Demon King and relying on a girl. The girl is the survivor of "Zeirishi", the only phantom occupation that can compete with tax angels.

(Source: Shogakukan, translated)