Sakurai Rihoko Arc, Chapter 1: Memories - S1.E17

Two years ago, Junichi asked his childhood friend Rihoko, to come and help him select a present for his date on Christmas Eve. Rihoko, who had an unrequited love for Junichi, was sad to find out later that he was stood up. In the present, Rihoko takes a shortcut to school through a hole in a fence, but gets stuck until Junichi helps pulls her out. Realizing she is gaining weight, she seriously swears to her friend Kanae that she'll go on a diet immediately, and gives her cupcakes to Junichi. Kanae seizes this chance to invite him and Masayoshi to go ice skating with them in the weekend. However, upon visiting her seniors at the Tea Club, Rihoko unwittingly breaks her diet there eating snacks until Manaka and Ruriko remind her. Eventually Junichi walks a sulking Rihoko home and even pass by and play on the slide where they and Miya played on as kids. After checking the scales that night, she swears to go on a diet.