Tarō Tatsunoko is the original creator behind the light novel series Problem Children Are Coming from Another World, Aren't They? (Japanese title: Mondaiji-tachi ga Isekai Kara Kuru Sō Desu yo?). This series, which Tatsunoko wrote, began publication on April 1, 2011, under the Kadokawa Sneaker Bunko imprint from Kadokawa Shoten, with illustrations by Yū Amano. The first part of the light novel series concluded on April 1, 2015, spanning twelve volumes. The story follows three youths with extraordinary psychic abilities who are summoned to a fantastical realm called Little Garden, where they use their powers in high-stakes competitions known as Gift Games to help restore a fallen community.

Following the conclusion of the initial series, Tatsunoko continued the narrative with a sequel light novel series titled Last Embryo, which began publication on June 1, 2015, under the same Kadokawa Sneaker Bunko imprint but with illustrations by momoco. This continuation maintains the setting and characters established in the original work.

The success of Tatsunoko's light novel series led to multiple adaptations. A manga adaptation illustrated by Rio Nanamomo was serialized in Kadokawa Shoten's Monthly Comp Ace magazine from September 2012. Another manga version, titled Mondaiji-tachi ga Isekai Kara Kuru Sō Desu yo? Z, was illustrated by Anri Sakano and ran in Fujimi Shobo's Age Premium magazine. An anime television adaptation produced by the studio Diomedea aired from January 11, 2013, to March 15, 2013, consisting of ten episodes, with an additional original video animation released later that year. The anime was subsequently licensed for North American distribution by Sentai Filmworks.

Information about Tatsunoko's creative process and artistic identity emerges from production notes related to the series. Tatsunoko initially conceived the story as a minimalist narrative set in an original universe, which led him to name the central setting Little Garden. However, after entering the Kadokawa Sneaker Equation Light Novel Contest, which placed significant value on worldbuilding, he expanded the setting considerably by incorporating extensive research on mythology, gods, and monsters. This approach proved successful, as he won the contest. Additionally, Tatsunoko originally intended for the story to take place entirely in an original fantasy world, but he ultimately incorporated characters from the real world to make the narrative more accessible, creating a compromise by having the protagonists come from different time periods: the past, present, and future.

The distinctive title Problem Children Are Coming from Another World, Aren't They? was not Tatsunoko's original choice. According to accounts of the series development, the title was actually the subtitle of another work submitted to the same literary contest, and a Kadokawa editor decided to assign it to Tatsunoko's series. Tatsunoko was reportedly surprised by this decision but accepted it on the grounds that the title would be more distinctive than his original choice.