Because this is a curse.

Unlike her beautiful twin sister Felicia, who is famous for her beauty, Martina is fat and ugly. On her fourteenth birthday, a capricious fairy cast a spell on her. A curse to become fat because she hated the beautiful twins. With her appearance completely changed, Martina spends her days being ridiculed by people outside the mansion. Her relationship with Rolf, a marriage candidate, is also terrible. In the meantime, her escort knight is always on her side. "Hehehe..." "——Miss Martina, you're scaring me. Your face." It seems the curse can be broken by a confession of true love, but...? A story about Martina, who does not 'grieve' over becoming fat. A heartwarming happy ending.