Sōshi Momoya teaches physics and leads the remedial tutoring class at Dimension High School, known for his consistent politeness and widespread popularity among the students. His life takes a drastic turn when a living meteorite named Spudio transports him and four students to an alternate dimension. There, they are forced into deadly puzzle battles against Sphinxes, entities that consume the souls of the defeated to ascend dimensions and threaten the world. During the battle against Sphinx Adihilas, despite the group solving the puzzles successfully, Momoya volunteers to be consumed, vanishing as a result.

Following his sacrifice, the students investigate his past and uncover his connection to Shiro Oide, a high school friend who died in a car accident. They discover Shiro was the reincarnation of Oedipus, the figure who guided Spudio to their world. This revelation places Momoya's actions within the larger context of loss and interdimensional conflict stemming from his history with Shiro.