Kenji Saitō is a Japanese creator known primarily as the original writer and creator behind the manga and anime franchise Trinity Seven. His professional background includes work as a scenario writer for visual novels and as a light novel author, and he is also the representative of the adult game company EX-ONE. He previously worked with the game studios feng and Windmill.

Saitō is best known as the creator of Trinity Seven, a fantasy romantic comedy series that began as a manga written by Saitō and illustrated by Akinari Nao. The series has been serialized in Fujimi Shobo's Monthly Dragon Age magazine since December 2010. The success of the original manga led to the expansion of Trinity Seven into a multimedia franchise, for which Saitō served as the original creator across various adaptations and spin-offs.

His direct involvement with the anime and film adaptations of his work is well documented. He wrote the screenplay for the 2017 anime film Trinity Seven: Eternity Library & Alchemic Girl. He also wrote the screenplay for the 2019 sequel film Trinity Seven: Heavens Library & Crimson Lord. On television, he is credited as the original creator and also contributed to series composition or scripts for certain episodes and the original video animation of the Trinity Seven anime series.

Beyond the main series, Saitō is credited as the original creator for numerous spin-off manga that expand the Trinity Seven universe. These include Trinity Seven: Levi Story, Trinity Seven: Lieselotte Chronicle, Trinity Seven: Seven Days, Trinity Seven: Revision, and Trinity Seven: Anastasia Holy Story, the latter of which was illustrated by Bcoca and ran from 2019 to 2021.

Saitō has also written several light novel adaptations of his own work. He wrote the Trinity Seven The Novel series, which explores additional backstory and events not covered in the original manga, with illustrations also provided by Akinari Nao. His involvement in the franchise extends to game design as well, as he is credited as the creator of the Trinity Seven RPG, a tabletop game based on his original setting.

Prior to his success with Trinity Seven, Kenji Saitō had an established career in the video game industry. His credits as a scenario writer for visual novels include titles such as Blessing of the Campanella, A Kiss for the Petals, and Looking for a Lost Future. He has also authored several light novel series outside of Trinity Seven, including The 101st Centennial Stories, The Saint's Sword and the Demon Dragon's World, and Miss Shiinamachi's Day of Safety.