The Ayin live independently, away from the Strigs, whom they perceive as dangerous sorcerers wielding dark magic. After settling into the forest near enemy territory, Vaedan accidentally steps into a magical trap cast by Uni. Vaedan warns Uni to stay on her side of the border, to which she reluctantly but respectfully agrees for the next four years. Uni often frolics by the shore, weaving shells into her hair and sketching animals, flora, and fauna that she finds fascinating. However, Vaedan is wary of her intentions. He watches her carefully from afar—even considers killing her to prevent potential harm to the land—and, despite the animosity, finds himself intrigued by her demeanor, intelligence, and beauty.

Vaedan discovers a part of the forest rotting in decay with animals gone rabid from its blight. He finds crushed shells in the area, suspects Uni's involvement. He confronts her, but when Uni denies any responsibility, she offers to help him investigate the cause. Vaedan reluctantly accepts, and together, with his wolf companion, Quul, and Uni's tiny dragon familiar, Yasumi, they attempt to uncover the mystery behind the blight.

Vaedan struggles with his distrust of Uni and the emotions he experiences around her—feelings that are unfamiliar to his Ayin culture. However, as they continue to work together and fight creatures affected by the decay, Vaedan begins to understand more of Strig culture and sees Uni not as an enemy, but as a respectable person who values protecting the forest above all things. Along the way, Uni sketches the unique fauna in Vaedan's territory, including sacred eong-fa flowers that the Ayins believe are blessed by the Earth Mother. Meanwhile, Vaedan takes note of his gradual loss of control over his thoughts and actions in Uni's presence.

They seek wisdom and advice from Nariya, an elderly Ayin who has a deep connection to the forest. She guides them to historical ruins, which Uni finds magical and sacred, where they find a corrupted lake and a ravaged sea newt. In a desperate battle, Vaedan forces Uni to destroy the ruins, thus destroying the apparent source of the decay. Seeing Uni upset over the destroyed ruins, Vaedan kisses her. When he pulls back, he is confused and blames Uni for casting a spell that forces him to act against his will. Frustrated, Uni leaves. Vaedan returns to Nariya, asking her to remove Uni's spell. Nariya laughs and explains that what he feels is not a spell but rather love, an emotion unknown to most Ayins since they live alone. Realizing his mistake, Vaedan goes back to the border to seek Uni, only to discover that she had left.

Months pass as Uni settles into Ota Village, a humble Strig village that has welcomed her assistance with everyday inconveniences. However, she notices Quul watching her from a distance, revealing that Vaedan had found her and was nearby. One day, she finds a dead deer on her doorstep, which prompts the Strigs, especially Kavi, to hunt the Ayin responsible for the perceived insult. When Uni discovers that the forest is still rotting, she musters the courage to confront Vaedan about the deer. Vaedan confesses his feelings, but Uni believes his feelings toward her are ingenuine, as Ayins do not know the meaning of love. However, she agrees to journey with him again to find and destroy the real source of the blight.

Their journey leads to Pitaya, an Ayin village known for trade and information. Uni poses as an Ayin, nearly revealing her enemy identity in an angry outburst against how the village treats a young, starving Ayin, Isan, who is struggling to survive in the infected forest. Isan shows them the rotten dragonfruit he collected, and Vaedan and Uni make a trade: food for information on where to find the blight.

Deeper in the forest, they find a corrupted dragonfruit tree dendrymph—a forest spirit that acts on the will of the Earth Mother. They realize the dendrymph has been corrupting itself in an attempt to kill the island's inhabitants, tired of the feud and unrest between Strigs and Ayins. They defeat the dendrymph, but Vaedan is critically injured in the fight. With Yasumi's help, Uni purifies the land with her magic, learns to “see” from the trees’ and forest’s perspective, and rids it of the blight.

Uni returns to the destroyed ruins in hopes of using the sacred lake and her newfound skill to speak to the Earth Mother. She finds three eong-fa flowers in Vaedan's bag and uses them as an equivalent exchange to plead for Vaedan's life and a second chance for the inhabitants on the island. The lake glows, accepting the offering and healing Vaedan.

When Vaedan awakens, he tells Uni that he loves her, offering her the last eong-fa flower as an apology and showing he is willing to break from tradition for her sake. Uni finally reciprocates. As they exit the ruins, they witness signs of nature's renewal, with new growth emerging from the formerly corrupted land. Realizing their adventure is coming to an end, Vaedan returns Uni's shell ornament to her hair and asks where she will go from here. Uni decides to return to the forest's edge, by the border near Vaedan's territory, and he happily agrees to this arrangement.