Ijimete Kureru Kimi ga Suki

Yuzuru Tachibana, a high school girl with family problems, is frustrated by her unsuccessful life. One day, she overhears her classmate, Kae Nijima, talking about an expensive coat her father bought her, and Yuzuru decides to target her for bullying. For a while, Yuzuru enjoys the bullying, but when her friends warned her that she'd be expelled if she gets caught, she loses interest and stops. However... even though Yuzuru is no longer instigating the bullying, Kae suddenly wets herself during class…

(Source: Ichijinsha, translated)