After being reincarnated into a fantasy world from modern Japan, a young man named Allen discovers he possesses a unique skill called Moon Gate. This ability allows him, and only him, to travel freely between his new fantasy home and the Japan of his previous life. Recognizing the potential of this power, Allen decides not to pursue the typical path of an adventurer or hero but instead launches a business venture. He uses the gate to transport modern goods and entertainment from Japan, selling them in the other world to people who are hungry for novelty and amusement.

The story follows Allen as he builds this cross-dimensional enterprise, beginning with small trades and gradually expanding his operations. His business brings him into contact with various figures in the fantasy world, including the daughter of a large corporation and a kingdom's princess, expanding his influence and personal connections. On the Japanese side of the gate, he receives support from associates such as Saionji and Akira, who assist with procurement and information.

As the narrative progresses into its second major arc, Allen's commercial reach grows significantly. He sets up a stall at a capital city fair, where he attracts the attention of Lei, the heir to a marquis family who purchases all of his products and grants him a mysterious medal that forges a new connection with the nobility. This encounter propels his business to a new level, integrating him deeper into the social and economic fabric of the fantasy world. The series chronicles his journey toward a leisurely and wealthy life, leveraging his unique position between two worlds for profit and comfort.