The Light Novel Proof: Pinpointing Subaru's Amnesia Span from Volume 22 to 25
The amnesia arc hits its darkest tone in Volume 23. While exploring the Taygeta Library, where the life histories of the deceased are cataloged into the Books of the Dead, the group stumbles upon the strangled corpse of Meili Portroute inside the Green Room. Because Subaru is mentally detached from his allies, the discovery triggers an Agatha Christie-style locked-room panic.
Subaru believes one of his companions is an unhinged killer. He hides Meili's body to prevent an immediate bloodbath, frantically scanning Beatrice, Emilia, and Ram for signs of betrayal. His panic deepens when he pulls a Book of the Dead bearing his own name from the library shelves. Opening it forces him to experience his own prior decapitations, freezings, and disembowelments from earlier arcs.
Seeing his past self die repeatedly convinced the amnesiac Subaru that "Natsuki Subaru" was not a normal person, but an unfeeling, obsessive strategist who discarded lives like pawns. This self-loathing became the central thematic hurdle of Arc 6. He was not merely trying to survive the Watchtower; he was fighting to avoid becoming the monster he believed his past self to be.