Samaru Ayuha is a high school student. She is honest and works hard at everything, no matter what. One day, she has trouble at a gyudon restaurant due to money. A man at the restaurant, Hiromitsu Yoshitaka, helps her out. The next day, she finds that Yoshitaka has come to her school as a substitute teacher for her ill homeroom teacher. Ayuha now believes that Yoshitaka is her fate in love. She keeps expressing her feelings to him. ~~ Adapted from the manga "Sensei Kunshu" (センセイ君主) by Koda Momoko (幸田もも子).