Kaiu Shirai is the pen name of a Japanese manga writer, best known as the creator of the internationally successful series The Promised Neverland. Shirai maintains a high degree of anonymity, with his real name and date of birth not publicly disclosed. He was born in Gifu Prefecture, Japan. As a student, he participated in traditional kabuki theater. After graduating from university, he worked at a standard company before resigning to pursue a career as a manga author full-time.

Shirai’s professional debut came in 2015 with the one-shot Ashley: Gate no Yukue, published in Shonen Jump+ with art by Rickey. The following year, he collaborated with artist Posuka Demizu for the first time on another one-shot, Poppy no Negai, which was released in February 2016. This collaboration proved successful and laid the groundwork for their major joint project.

The idea for The Promised Neverland originated from a lengthy manuscript that Shirai had written while still an amateur. In late 2013, he submitted a 300-page draft to Shueisha, which covered approximately fifteen episodes and concluded with the children's escape from Grace Field House. The original title was "A Way for Us to Survive in This World," a phrase later referenced in the published series. Editor Takushi Sugita was convinced by the draft, and together they spent two years refining the concept and searching for an artist, as Shirai preferred to focus solely on writing. The duo finally found Posuka Demizu, and their partnership was officially formed.

The Promised Neverland was serialized in Weekly Shonen Jump from August 2016 to June 2020, spanning a total of twenty volumes. The series became a critical and commercial hit, winning the Shogakukan Manga Award for best shonen manga in 2018. Its success led to a prominent anime adaptation. The first season of the anime aired in January 2019, receiving widespread acclaim for its faithful and suspenseful storytelling.

Following the conclusion of The Promised Neverland, Shirai has continued to work as a writer for Shueisha. In January 2024, he published a one-shot titled Kubigeshō with illustrator Shiki Hamada in Weekly Shonen Jump. Later that year, in December 2024, he released another one-shot, Apple, with art by Yoichi Amano.

Shirai’s work is defined by psychological suspense, intricate strategic plotting, and a focus on the bonds of family and friendship in the face of overwhelming despair. He has cited manga artists such as Osamu Tezuka, Naoki Urasawa, and Yoshihiro Togashi, as well as film directors Akira Kurosawa and Hayao Miyazaki, as major influences on his work. In the industry, Shirai is noted for his deliberate approach to narrative structure, having conceived the entire story arc of The Promised Neverland before serialization began. This method, along with his commitment to preserving the dark and complex themes of his story within the context of a Weekly Shonen Jump series, has established him as a significant figure in modern manga writing.