Saisou is a Japanese manga artist and illustrator. Active under the name Saisou for their manga work, they also work as an illustrator under a separate name, though their primary creative identity is as the author of several manga series. Their birthday is February 15.

Saisou is best known as the original creator of the romantic comedy manga Story of a Small Senior in My Company, also known as My Tiny Senpai. The series began serialization in Takeshobo’s Storia Dash web manga service in April 2020. As of February 2025, the ongoing series has been compiled into ten tankōbon volumes. The work gained significant popularity, leading to multiple adaptations. An anime television series adaptation produced by Project No.9 aired from July to October 2023, followed by a live-action television drama that aired from January to March 2025.

Prior to this work, Saisou authored the series The Handsome Girlfriend and the Heroic Me!, which was published by Kodansha and ran for 16 chapters, with its first compiled volume released in March 2020. They also produced a romantic comedy short story collection titled Shall We Kiss?, which was published in November 2020.

Saisou’s artistic identity is closely tied to the romantic comedy genre, with a focus on workplace and interpersonal dynamics often featuring a contrast in character statures and personalities. Their most prominent work, Story of a Small Senior in My Company, centers on the sweet interactions between a kind, diminutive senior colleague and her new junior employee, establishing a signature style of lighthearted, character-driven storytelling.