Rina Saegusa is a chubby girl with low self-confidence. She tries lifting a barbell with all her might at her family's struggling gym, but she's no match for it. However, at that very moment, she crosses paths with the ancient world! Plato, the master of muscular physique from ancient Greece, possesses Rina's body! Plato then guides Rina through the process of building her body from scratch. Will Rina be able to change by following his teachings? And what will become of her family's gym?