"My Ex-Boyfriend Loves Boys' Love!" centers on the unexpected reunion of two former lovers, Haruto and Shun, whose relationship ended years ago. Haruto, now a successful manga editor, discovers that Shun has become a popular Boys' Love (BL) manga artist under the pen name "Shunpei." The twist is that Shunpei's works are heavily inspired by their past relationship, with Haruto unwittingly serving as the muse for the stories. This revelation forces Haruto to confront unresolved feelings and the complexities of their shared history.

As Haruto begins working with Shunpei professionally, the dynamic between them grows increasingly tense. Shunpei's candid portrayal of their past in his manga forces Haruto to reflect on their breakup and the emotional distance that drove them apart. Meanwhile, Shunpei uses his art as a way to process his lingering feelings for Haruto, creating a narrative within the manga that mirrors their real-life struggles. The story explores themes of love, regret, and the blurred lines between fiction and reality, as both characters navigate their evolving relationship.

The supporting cast includes colleagues and friends who provide insight into Haruto and Shunpei's personalities and histories. These characters often serve as sounding boards for the protagonists, offering perspectives that challenge their assumptions and push them toward growth. The interplay between the professional and personal lives of Haruto and Shunpei adds depth to the narrative, highlighting the challenges of balancing creative expression with emotional vulnerability.

The manga blends humor, romance, and introspection, using the framework of BL storytelling to examine the complexities of human relationships. The meta-narrative, where Shunpei's manga reflects their real-life experiences, creates a layered storytelling approach that invites readers to consider the parallels between art and life. Through its exploration of love, identity, and the creative process, "My Ex-Boyfriend Loves Boys' Love!" offers a nuanced portrayal of two individuals rediscovering each other and themselves.