Miyakokasiwa is a Japanese manga artist known primarily for illustration work on several manga series, often in collaboration with separate writers. The creator is best known for illustrating the manga Battle Game in 5 Seconds, which was adapted into an anime television series that aired from July to September 2021. For this series, Miyakokasiwa is credited as the manga illustrator, with the story credited to Saizō Harawata. The manga began serialization in Shogakukan's MangaONE app and Ura Sunday website in August 2015 and has been collected into multiple tankōbon volumes. In the anime adaptation, Miyakokasiwa received credit for the original manga as well as for original character design.

Beyond Battle Game in 5 Seconds, Miyakokasiwa has contributed as the artist for several other manga adaptations. The creator illustrated The Testament of Sister New Devil, a manga series based on the light novels written by Tetsuto Uesu. This series was published in English by Seven Seas Entertainment and in French by Delcourt. Miyakokasiwa also served as the artist for Bestia, a manga written by Makoto Sanda and published by Yen Press. Library catalog records confirm Miyakokasiwa as the author entry for these published works.

The pattern across Miyakokasiwa's career shows a consistent role as a manga illustrator adapting stories from other creators or collaborating with writers, rather than originating the narratives. The artistic identity is tied to action-oriented shonen manga with supernatural or fantasy elements, as seen in the superpowered battles of Battle Game in 5 Seconds, the demonic conflicts of The Testament of Sister New Devil, and the cryptid-hunting premise of Bestia. In the industry, Miyakokasiwa holds significance as the artist for Battle Game in 5 Seconds, which achieved an anime adaptation and has seen ongoing serialization since 2015, with the manga briefly placed on hiatus in late 2024 due to health issues before resuming in January 2025.