"21 Emon" is a science fiction comedy series set in a futuristic world where advanced technology coexists with everyday life. The protagonist, 21 Emon, is a young boy who works at his family's traditional inn, the Tsuzureya, located in the bustling city of Uratown. Despite the inn's outdated appearance, it attracts a variety of eccentric guests, including aliens, robots, and time travelers, due to its reputation for hospitality.

The narrative revolves around 21 Emon's daily adventures as he manages the inn and interacts with its peculiar clientele. His life takes a turn when he encounters Monga, a bumbling alien prince from the planet Monga, and Gonsuke, a sentient robot with a penchant for mischief. Together, the trio forms an unlikely friendship and embarks on a series of comedic escapades, often involving misunderstandings, technological mishaps, and encounters with bizarre characters.

Throughout the series, 21 Emon's resourcefulness and kindness are tested as he navigates the challenges of running the inn while dealing with Monga's incompetence and Gonsuke's antics. The stories often blend humor with lighthearted social commentary, exploring themes of coexistence, cultural differences, and the clash between tradition and modernity. The episodic nature of the series allows for a wide range of scenarios, from time-traveling adventures to encounters with alien royalty, all while maintaining a focus on the quirky dynamics between the main characters.

The setting of Uratown serves as a vibrant backdrop, filled with futuristic gadgets, flying vehicles, and a diverse population of humans and extraterrestrials. Despite the advanced technology, the series retains a nostalgic charm, emphasizing the importance of human connection and the value of traditional hospitality. The interactions between 21 Emon, Monga, and Gonsuke drive the narrative, creating a balance of humor, heart, and imaginative storytelling that appeals to a broad audience.