Hiro Yūki is a Japanese writer recognized as the original creator behind the light novel series 20 Seiki Denki Mokuroku, which has been adapted into the anime television series Sparks of Tomorrow. Hailing from Shiga Prefecture, Yūki is an author whose published works include the light novel 20 Seiki Denki Mokuroku, which debuted in 2018. This was followed by the novel Mobomoga in 2020 and the ongoing series Imari-san wa Tabi Jougo, which began publication in 2025. The most prominent work associated with Hiro Yūki is 20 Seiki Denki Mokuroku, also known as 20th Century Electricity Catalog. The story is set in an alternate version of the early twentieth century where technological development is dominated by steam power. The narrative follows a boy who has become distrustful after the death of his brother and a devout girl harboring regrets for her deceased mother. Together, they seek to uncover the secrets of the 20th Century Electrical Catalog, a document that offers a glimpse into a future powered by electricity. This light novel was announced for an anime adaptation under the English title Sparks of Tomorrow. The official staff listing for the anime production credits Hiro Yūki as the original work creator, with the novel published under the KA Esuma Bunko imprint, which is associated with Kyoto Animation. The anime series is scheduled to premiere in July 2026. As a creator, Hiro Yūki is defined by this novel and its subsequent adaptation, marking their entry into the anime industry as an original intellectual property holder.