Naofumi Iwaya (voiced by Kaito Ishikawa) is a young man with a strong sense of justice in his heart. He is deeply angry about many unfair things happening in the world. By chance, he was teleported to another world and became the Shield Hero who can use a variety of shields with different functions. He thought he could start his journey of justice, but he was betrayed by his comrades just a few days ago and lost all his belongings. Naofumi vowed never to trust anyone in this world again. At this juncture, a girl named Raphtalia (voiced by Asami Seto) appeared in front of Naofumi. Raphtalia was a slave. Naofumi decided to buy her in exchange for loyalty with money. In the process of getting along, Raphtalia gradually fell in love with her master.