"Itsuka Tenma no Kuro-Usagi" (also known as "A Dark Rabbit Has Seven Lives") is a supernatural fantasy anime based on the light novel series by Takaya Kagami. The story centers on Taito Kurogane, a high school student who discovers he is the reincarnation of a powerful being known as the "Dark Rabbit." This revelation comes after he encounters Himea, a mysterious girl who claims to have been searching for him for over a thousand years. Himea is revealed to be a vampire and a key figure in Taito's past life, where he was a warrior tasked with protecting her.

The narrative unfolds as Taito learns about his past life and the responsibilities tied to his reincarnation. He is drawn into a conflict involving supernatural entities, including vampires, demons, and other mythical beings. These factions are vying for control over a powerful artifact known as the "Eclipse," which holds the potential to reshape the world. Taito's connection to the Dark Rabbit grants him unique abilities, but it also makes him a target for those seeking to exploit his power.

As the story progresses, Taito forms alliances with various characters, including Gekkou, a demon swordsman, and Mitsuki, a childhood friend who becomes entangled in the supernatural events. The relationships between these characters are tested as they navigate the dangers of their world and uncover deeper truths about their identities and the Eclipse. The plot is driven by a mix of action, mystery, and emotional drama, with Taito's journey of self-discovery serving as the central focus.

The anime explores themes of reincarnation, destiny, and the struggle between light and dark forces. Taito's growth as a character is marked by his efforts to reconcile his past life with his present identity while protecting those he cares about. The series balances its supernatural elements with moments of humor and camaraderie, creating a dynamic narrative that appeals to fans of fantasy and action genres.