"The World God Only Knows: Magical Star Kanon 100%" is a two-episode OVA that serves as a continuation of the main series, focusing on the idol character Kanon Nakagawa. The story is set within the framework of the original series, where Keima Katsuragi, a high school student and master of dating sim games, is tasked with capturing "runaway spirits" that hide in the hearts of real girls. These spirits cause emotional instability, and Keima must make the girls fall in love with him to expel the spirits.

In this OVA, Kanon Nakagawa, a popular idol and one of Keima's previous conquests, is preparing for a major concert. However, her excitement is overshadowed by a lingering runaway spirit that resurfaces, causing her to experience intense emotional turmoil. The spirit amplifies her insecurities and fears, particularly her anxiety about performing in front of a large audience and her unresolved feelings for Keima. As her emotional state deteriorates, her ability to perform is jeopardized, threatening the success of her concert.

Keima, accompanied by Elsie, his demon partner, is once again called upon to resolve the situation. Using his expertise in understanding and manipulating emotions through his gaming skills, Keima devises a plan to help Kanon confront her fears and expel the spirit. The narrative explores Kanon's internal struggles, her dedication to her career, and her complex feelings for Keima, blending moments of humor, drama, and emotional depth.

The OVA maintains the series' signature balance of lighthearted comedy and heartfelt character development, with a focus on Kanon's growth as an individual and an idol. It also reinforces the overarching themes of the series, such as the importance of understanding and addressing one's emotions, while providing a self-contained story that complements the main narrative. The interactions between Keima and Kanon highlight their unique dynamic, showcasing Keima's strategic approach to solving emotional conflicts and Kanon's determination to overcome her challenges.