Four years after they broke up, mathematics teacher Lin Zhou unexpectedly became the class teacher of his ex-girlfriend Su Xiaotang's cousin. As soon as he became a friend, Su Xiaotang showed no respect at all and asked him to pay back the unpaid milk tea money that year. Lin Zhou was unwilling to show weakness and took revenge in the name of "educating" his cousin. Su Xiaotang was frequently called to school because she was playing with her mobile phone in class and did not finish her homework. In their daily tit-for-tat exchanges, old feelings quietly fermented, full of sweetness and laughter.
