"The Tale of Outcasts" is a fantasy anime set in an alternate version of early 20th-century England, blending historical elements with supernatural themes. The story centers on Wisteria, a young orphan girl living in a world where humans coexist with demons, known as "Outcasts." These demons are often feared and ostracized by society, despite their ability to grant humans extraordinary powers in exchange for contracts. Wisteria, who has endured a life of hardship and loneliness, forms a bond with Marbas, a powerful and enigmatic demon who has lived for centuries. Marbas, once a feared and respected figure among demons, has grown weary of his immortal existence and seeks purpose in his connection with Wisteria.

The narrative explores their evolving relationship as they navigate a world filled with prejudice, danger, and political intrigue. Wisteria and Marbas encounter various factions, including the Church, which views demons as threats to humanity, and other demons with their own agendas. As they travel together, they uncover secrets about Marbas's past and the true nature of the contracts between humans and demons. The story delves into themes of belonging, identity, and the moral complexities of power, as Wisteria and Marbas challenge societal norms and confront their own vulnerabilities.

The main characters are defined by their struggles and growth. Wisteria, initially portrayed as fragile and dependent, gradually develops resilience and determination, driven by her desire to protect those she cares about. Marbas, despite his immense power, grapples with existential questions and the weight of his long life, finding solace in his bond with Wisteria. Supporting characters, including other demons and humans, add depth to the narrative, each contributing to the exploration of the series' central themes. The plot balances episodic adventures with an overarching storyline, creating a cohesive and engaging tale of camaraderie and defiance in a world that marginalizes the unconventional.