The protagonist, Sawaguchi Makoto, is a high school girl who has lived her entire childhood in a tense, unhappy home, constantly holding herself back for the sake of her constantly arguing parents. When they eventually divorce, she is deeply wounded to find that neither parent views or treats her as part of their new lives. Feeling utterly alone and unwanted, she wanders to a certain shrine where she is drawn by a strange, inexplicable voice. Following the call, she encounters a strikingly handsome man with cold, piercing eyes named Ryuuka. Almost immediately, an enormous black serpent appears beside him, revealing Ryuuka's true nature as a snake god. Before she can fully process the situation, Ryuuka declares that she is his bride, and Makoto is pulled into a surreal, contractual marriage with the reclusive and mysterious deity.

The story is set in a contemporary Japanese world that borders the hidden, supernatural domain of the snake god clan. Ryuuka is initially emotionally distant and cold toward his new human bride, and both parties regard the marriage as a purely formal arrangement. However, their relationship begins to shift when Ryuuka reveals that Makoto is not his first bride, a confession that stirs unexpected feelings in her. As Makoto starts living in Ryuuka’s world, she is gradually introduced to his snake god family, including a number of powerful and eccentric relatives. Her earnest and resilient personality begins to thaw Ryuuka’s icy demeanor, and she slowly comes to see him as someone who also craves warmth and connection.

The narrative deepens as Makoto becomes more integrated into the supernatural family. The central conflict escalates when she and Ryuuka decide to visit the grand uncle, the patriarch who rules over the entire snake god clan, to seek his counsel on their marriage. The grand uncle, who harbors a strict and traditional mindset, demands that Ryuuka become the master of the mountain, a position of immense power and responsibility. When Ryuuka and Makoto attempt to navigate this demand, the grand uncle responds with anger, leading to a confrontation where Makoto is captured. This event forces Ryuuka to take a stand to protect her, pushing their relationship and the family’s politics toward a climactic resolution. Throughout the series, the core theme revolves around Makoto’s quest for the gentle, loving family she has always wanted, ultimately finding that family may not be defined by blood, but by the bonds she forges in an unexpected place.