"D.C. III ~Da Capo III~" is a 13-episode anime series set in the fictional Hatsunejima Island, a recurring location in the Da Capo franchise. The story unfolds in a world where cherry blossom trees bloom year-round, a phenomenon tied to the island's magical properties. The narrative centers on Kiyotaka Yoshino, a high school student who transfers to Kazami Academy, a school known for its mysterious traditions and supernatural occurrences. Kiyotaka becomes involved with the Newspaper Club, a group of students tasked with investigating and documenting the island's peculiar events.

The series introduces a diverse cast of characters, each with unique connections to the island's magic. Rikka Hiiragi, the club president, is a cheerful and determined leader who harbors a deep curiosity about the island's secrets. Sara Rukawa, a quiet and reserved girl, possesses the ability to see the future through dreams, while Himeno Katsuragi, a childhood friend of Kiyotaka, is deeply tied to the island's history and its magical cherry blossom tree. Other members of the club include Charles Yoshino, Kiyotaka's younger sister, and Aoi Hinomoto, a cheerful and energetic girl who often lightens the mood.

As the story progresses, the Newspaper Club uncovers the existence of "Witches," individuals who wield magical powers tied to the island's cherry blossoms. These Witches are bound by a curse that causes them to disappear once their powers are fully realized. The central conflict revolves around the club's efforts to understand and potentially break this curse, which threatens the lives of those they care about. The narrative explores themes of friendship, sacrifice, and the passage of time, as the characters grapple with the consequences of their actions and the inevitability of loss.

The plot intertwines personal struggles with the overarching mystery of the island, blending slice-of-life moments with supernatural elements. Kiyotaka's relationships with the club members deepen as they work together to uncover the truth behind the Witches and the cherry blossoms. The series concludes with a resolution that ties together the characters' arcs while leaving room for interpretation regarding the island's future and the lingering effects of its magic.