Just as the famous writer Sensei is about to accomplish his life ambition and commit double suicide with his lover Sacchan, he is hit by a truck and transported to another world. Deemed an adventurer by the local priestess Annette, Sensei is given the daunting mission of slaying the demon king. Refusing to play into his new role, Sensei decides his efforts are better served looking for Sacchan in the hope that she is somewhere in this new world. Early on in his journey, Sensei crosses paths with the martial artist Tama and unexpectedly saves her from mortal peril. Grateful for his actions, Tama decides to escort him. The pair are soon joined by Annette who, seduced by the writer's strong personality, has sworn to protect Sensei's life. As the unlikely trio wander the dangerous, monster-infested lands, they soon realize that human beings might be the true threats to the peace of the world—and Sensei might be the only one with the power to stop them.

After a fatal encounter with a truck, Takafumi Takaoka's uncle, Yousuke "Ojisan" Shibazaki, lies comatose for 17 years. When he finally regains consciousness, Ojisan begins to ramble in a foreign tongue and reveals that he had been transported to a magical world called Gran Bahamal. Takafumi dismisses his uncle's claims as nonsense until an incantation makes a cup of water hover in the air. In a flash of brilliance, the pair creates a YouTube channel to showcase Ojisan's magical abilities. The responsibility now falls on Takafumi's shoulders to acquaint Ojisan with everything that has transpired during his absence, including getting him up to speed with the internet, new technology, and surprisingly, the outcome of the '90s console war—the result of which was especially distressing for a hardcore SEGA fan. With Ojisan's wisdom from his other world experiences, they grow their YouTube channel and tackle online comments and trolls. The journey of this uncle-nephew duo promises to be anything but conventional.