Natsu Hyūga is a pseudonymous Japanese novelist best known as the original creator of the internationally successful franchise The Apothecary Diaries. The name Hyūganatsu is a pen name, which the author has confirmed is rendered as a single word rather than a given name and family name. The name was chosen because it is the name of her favorite fruit, adopted at the suggestion of an editor after she initially published her work under the name Uribō. She is a native of Fukuoka Prefecture and continues to reside there.

Hyūga began her career by publishing The Apothecary Diaries on the user-generated novel website Shōsetsuka ni Narō in October 2011. She has stated that she did not originally aim to become a professional writer, having written novels as a student for pocket money. After considering careers such as a police officer or a farmer, she became an ordinary company employee. The catalyst for writing The Apothecary Diaries was the Great East Japan Earthquake in 2011, which led to a lack of entertainment and prompted her to explore the Shōsetsuka ni Narō website out of boredom.

The initial concept for The Apothecary Diaries was markedly different from the final work. Hyūga originally conceived a story about a mother with three children living in a gloomy mining town, solving mysteries related to poisoning. She changed the setting to the glamorous imperial rear palace and the protagonist to a young apothecary after considering that the website’s users favored younger protagonists and fantasy settings. The character of Jinshi, the central male lead, was also originally intended to be killed off, but Hyūga changed this plot point due to significant reader affection for the character, demonstrating her responsiveness to audience feedback.

The Apothecary Diaries was first published as a single-volume novel by RayBooks in 2012 before being re-launched as an ongoing light novel series by Hero Bunko in 2014, with illustrations by Touko Shino. The series has since expanded into multiple media. Two separate manga adaptations began serialization in 2017. One is published by Square Enix in Monthly Big Gangan, and another is published by Shogakukan in Monthly Sunday Gene-X. A television anime adaptation produced by OLM and Toho Animation began airing in October 2023, with a second season following in January 2025. As of March 2025, the combined sales of the light novel and manga series, including spin-offs, have surpassed 40 million copies.

Beyond The Apothecary Diaries, Hyūga has authored numerous other light novel and novel series. These works span a range of genres and include King of Tonelico, Kurimiko Ayakashi Yobanashi, Nazotoki Iseki Hakkutsubu, Requirements for a Crack Detective, The Son of the Immortal King, and The Failure at God School. Many of these titles have also been adapted into manga series, such as The Failure at God School and You Can't Bluff the Sharp Eyed Sister.

Hyūga maintains a private public persona, never showing her face. For fan events and public appearances, she wears a boar costume based on her online avatar, Uririn. Her creative process is notably collaborative with her audience; she writes serially on Shōsetsuka ni Narō and has adjusted major plot points, such as Jinshi’s fate, based on reader reactions. She has stated that while she keeps the main trunk of the story the same, she sees no need to write material that her readers do not enjoy. She continues to write The Apothecary Diaries, describing the first published volumes as a potential ending point while she searches for a satisfying conclusion to the continuing narrative.