Rei Kagami (Ryosuke Yamada) is a billionaire and the CEO of the leading conglomerate company Kagami Group. He is an extremely smart inventor, who has developed revolutionary products, and is now doing research on high precision AI. When he was little, he was a curious and kind kid. As he grew up, his curiosity remained, but he became self-centered. For certain reasons, he begins to teach at a school, while hiding his identity as a billionaire and the CEO of Kagami Group. His performance as a teacher is quite poor compared to his excellent work as a CEO. He is incapable of understanding the ordinary lives of the teachers and students around him.