"Zettai Shōjo Seiiki Amnesian" is a manga series that blends elements of fantasy, adventure, and psychological drama. The narrative centers around a young boy named Kaito, who finds himself transported to a mysterious and otherworldly realm known as Amnesian. This realm is inhabited by enigmatic beings called "Absolute Girls," who possess extraordinary powers and are bound by a rigid hierarchy. The Absolute Girls are tasked with maintaining the balance of Amnesian, a world that exists in a state of perpetual twilight and is governed by its own set of surreal rules.

Kaito's arrival in Amnesian disrupts the delicate equilibrium of this world. He is quickly identified as an "Outsider," a rare individual who does not belong to the realm but has the potential to influence its fate. The Absolute Girls, each embodying distinct traits and abilities, are divided in their reactions to Kaito's presence. Some view him as a threat to the established order, while others see him as a catalyst for change. Among them, a girl named Lacia emerges as a central figure. Lacia, who wields the power of memory manipulation, becomes Kaito's guide and protector, though her motivations remain ambiguous.

As Kaito navigates Amnesian, he uncovers fragments of his own forgotten past, which are intricately tied to the origins of the realm. The Absolute Girls, too, grapple with their own fragmented memories and identities, hinting at a deeper connection between the Outsider and the world he has entered. The story delves into themes of identity, memory, and the nature of reality, as Kaito and the Absolute Girls confront the enigmatic forces that govern Amnesian. The narrative is punctuated by moments of tension and revelation, as alliances shift and the true purpose of Kaito's presence in Amnesian is gradually unveiled.

The manga explores the interplay between the characters' personal struggles and the larger mysteries of the world they inhabit. Kaito's journey is marked by his interactions with the Absolute Girls, each of whom represents a different facet of the realm's complex society. Through these interactions, the series examines the consequences of power, the fragility of memory, and the search for meaning in a world that defies conventional understanding. The story builds toward a climactic confrontation that challenges the very foundations of Amnesian, leaving the fate of its inhabitants—and Kaito himself—uncertain.