"Beta Entry Forbidden": A secretive community app where only Alphas and Omegas can connect. During the bustling rush hour, a provocative post suddenly appears on the app's anonymous message board: "An Omega in heat has been let loose on the subway heading ** from OO. If you happen to be on the same train, hurry up, catch them, and have a great time! ^^" Encouraged by the post, nearby Alphas begin hunting for the Omega ready for mating. Meanwhile, Haeyoung, caught off guard by a sudden heat, finds himself trapped in this game of tag. Will he manage to escape unscathed?