I'm pretty, and she's ugly.

Since middle school, Maimi and her friends have competed for beauty and bullied their less attractive classmates. Even when they reunite at a class reunion as adults, they show no signs of remorse and each appear to be living a happy life. However, they learn that one of their group members, Namiko, has committed suicide...? A thrilling suspense story in which a false friendship leads to a countdown to death!!

(Source: Seisensha, machine translated)

Original Japanese:
cmoa (Chapters, Volumes)