Cadis Etrama di Raizel, known as Rai, enrolls at Ye Ran High School under the guise of a student to evade the Union, a dangerous group hunting him. Despite trying to blend in and understand human routines, Rai's tranquility is shattered when he must rescue his classmates from the clutches of the Union. Simultaneously, M-21, a former Union agent turned school security member at Ye Ran, grapples with his past loyalties and the risks of his rebellion. Adding to the complexity, Nobles Regis K. Landegre and Seira J. Loyard arrive at the school to probe into Rai's identity. As the Union intensifies its pursuit of M-21 for crucial information, Rai must safeguard his secrets and loved ones without revealing his true nature.