On a strange night on Earth, an engineering student was snatched from his world, seemingly killed, and brought to a place between dimensions. There, a masked creature called System offered him a choice: move on, or take over the body of someone who was dying in another world. He chose a fox-like boy named Vonn, who had a sister and parents already mourning him and unaware that their revived, wildly ambitious family member was now someone else. Not wanting to break their hearts, he explained his odd knowledge as a divine vision.

The old Vonn already had a reputation as an ambitious would-be engineer, in a world where the System imposed rules of magic and skill advancement. The new Vonn took to this life quickly by becoming an inventor using his Earth knowledge. He made friends including the master Smith named Urika, who helped him start the seed of an industrial workshop; the Bard named Kotta, who wanted to spread stories from the other world; and bird-girl Selen... who was secretly just like him. Vonn and Selen conspired to advance this world's technology along with literacy and other aspects of their old life, but it would take time.

Eventually Kotta and Vonn's sister Tazo learned of the outsiders' true origin, to their unease and the Bard's fascination. Tazo reluctantly accepted that this new Vonn was in some sense the same person as her brother. Kotta was part of the Kobold race who tend to follow a minority religion involving four seasonal Dragons, and he's become convinced that Earth's stories are the key to a religious reformation.

While building things like bicycles and a type of magical engine, Vonn learned of a prisoner who also knew the alien tongue called English. Worse yet, there was evidence that he was being held in a dungeon where dark, highly illegal rituals were in progress. With the patronage of his local baron, Vonn and his friends built the first-ever airplane, and used it for a scouting mission to bring a spy to the dungeon. One crash later, Vonn and the spy stand at a tunnel entrance. They're looking for hard proof of a crime, and for a way to find the prisoner.

Characters (partial list):

-Vonn: Formerly a human engineering student, now a fox-like inventor in another world.

-Tazo: Sister of the original Vonn, who's mostly accepted Vonn as her brother despite knowing the truth.

-Selen: Also from Earth, now a bird-like alchemist whose family runs a postal business.

-Kotta: kobold friend of Vonn. An aspiring bard.

-Urika: kobold forgemaster and business partner of Vonn.

-Baron Bogstep: ruler of Vonn's town and several others. Funds Vonn's operations.

-Brightstep: Son of Bogstep, magic-user and reluctant bureaucrat in training. Now a friend of Vonn.