Masamune Tōya is one of the older residents aboard the airship Norn and serves as a dependable older brother figure to the younger members of the crew. He is intelligent and well-read, possessing a broad range of knowledge, but he is notably clumsy and unskilled with his hands, often finding himself in awkward situations despite his sharp mind. His appearance includes orange undercut hair and hazel eyes, and he typically wears a white shirt with blue designs beneath a black cape. He always wears gloves, which are related to controlling his special ability.

His ability allows him to see into the past, a power that makes him valuable for investigation and understanding hidden events. Because of this, the organization known as the World entrusts him with the task of uncovering the traitor among the passengers. Tōya is originally from the same island as Natsuhiko Azuma, and as a descendant of the scientists who created the being known as Aion, he already knows the true purpose of the journey, the nature of the World, and the existence of the reset from the beginning. He acts as a voice of reason and leadership, often mediating disputes among the group to maintain harmony.

He has a good relationship with Kakeru Yuiga and warmly welcomes Koharu when she arrives on the ship. His route in the story is only accessible when Koharu is selected as the protagonist, and through that story his mysterious background and perspective as an islander are explored in depth. While he initially operates in the background, his role becomes more central as the truth behind the voyage is revealed, and his sense of responsibility and protective nature drive his actions throughout the narrative.