My younger sister's modest revenge for always being bullied by her older sister—you'll forgive her this much, won't you? My merciful older sister.

The younger sister discovers that her older sister, who had always been kind to her, was actually looking down on her as a failure. The beautiful older sister, the plain younger sister. The younger sister was also inferior in magical power. However, the younger sister thought it was cruel for her sister to pretend to be kind while mocking her. When confronted about it, the older sister would evade the issue. The younger sister was fed up with her sister's good public image. Then, when the older sister became jealous that the younger sister had been chosen as the crown prince's fiancée, she seduced him and had the engagement broken off, taking her place. What revenge did the younger sister take on her older sister after learning this?