While Kim Jaeha and Yun Se-i were childhood friends, they started to drift apart as they grew older. Due to strict parents who set extreme restrictions, the two have formed a secret alliance where they act like best friends in front of their parents, but become total strangers when out of their sight. Nonetheless, Jaeha secretly harbors feelings for Se-i.

Soon, Jaeha and Se-i face difficulties when Se-i's mother asks them to perform a song together as a couple at her second wedding. The pair hesitantly decides to humor the request, only to end up in more complicated situations. However, all of these troubles are advantageous to Jaeha as he tries to make Se-i reciprocate his feelings.

Our Secret Alliance is originally a webtoon series that was published in book format by Dasan Books (다산북스) from February 26, 2024, to February 14, 2025. It has been published digitally in English by Webtoon Entertainment since May 6, 2022.