Natsume and Mikami-sensei are boyfriend and girlfriend in secret. Wanting to enjoy lovey-dovey days with Natsume, Mikami-sensei refused to become a general manager for his dad's company and made an outrageous declaration: "I'll become a high school student!!" No one could have expected that Mikami-sensei would become a high school student in the name of love! And so, a rowdy high school life that involves even Shiro-kun and the other two Mikami brothers begins☆