"Mon Seul" is a manga series that explores themes of identity, love, and the complexities of human relationships within a supernatural framework. The narrative centers on a young man named Shuu, who possesses the unique ability to see the "threads of fate" that connect individuals to their destined partners. These threads manifest as glowing, ethereal strands visible only to him, symbolizing the bonds between people. However, Shuu himself is unable to see his own thread, leaving him isolated and uncertain about his own destiny.

The story begins with Shuu leading a solitary life, burdened by his ability and the emotional weight of witnessing the connections of others while remaining disconnected himself. His perspective shifts when he encounters a mysterious girl named Aoi, who claims to have no thread of fate at all. Intrigued by her anomaly, Shuu becomes drawn to Aoi, and their relationship forms the core of the narrative. As they grow closer, Shuu begins to question the nature of fate, free will, and whether the threads he sees truly dictate the course of people's lives.

Throughout the series, Shuu and Aoi navigate their evolving bond while confronting external challenges. Aoi's lack of a thread attracts the attention of supernatural entities that seek to exploit her unique condition, forcing the pair to confront dangers that test their resolve. The story delves into the origins of Shuu's ability, revealing a deeper connection to the metaphysical forces governing fate. As Shuu uncovers the truth about his power and its implications, he must grapple with the moral and emotional consequences of interfering with the threads he sees.

The supporting cast includes individuals whose lives intersect with Shuu and Aoi, each contributing to the exploration of the series' central themes. These characters often serve as foils, highlighting the contrast between those who embrace their fated connections and those who resist or redefine them. The narrative weaves together moments of introspection, action, and emotional tension, creating a layered exploration of human relationships and the concept of destiny.

"Mon Seul" balances its supernatural elements with a focus on the emotional and psychological struggles of its characters. The interplay between Shuu's ability and his personal journey forms the backbone of the story, offering a nuanced examination of how individuals navigate love, loss, and the search for meaning in a world where fate and choice are inextricably linked.