[1][2] On 21 June 2015, Kaiu Shirai published his first professional work, a standalone piece called, The Location of Ashley-Gate, in Shōnen Jump+, a digital imprint of Shueisha, with art by Kyousuke Maruyama.

[3] Again, in the same magazine, he published his second work, another standalone piece called, Poppy's Wish, in collaboration with artist Posuka Demizu on 18 February 2016.

[11] On 6 January 2024, Kaiu Shirai along with illustrator Shiki Hamada launched a standalone one-shot, titled Kubigeshō, in the combined Issue #6–#7 2024 of Weekly Shōnen Jump.

[12] Within the same year, on 9 December, Kaiu Shirai along with illustrator Yōichi Amano launched a standalone one-shot, titled Apple, in Issue #2 2025 of Weekly Shōnen Jump.

[13] Kaiu Shirai commented that he was influenced by manga artists Osamu Tezuka, Naoki Urasawa, Yoshihiro Togashi and Eiichiro Oda; as well as directors Akira Kurosawa, Kōki Mitani, Kentaro Kobayashi and Hayao Miyazaki.