Noroware Oujo no Fukushuu wa Koushaku-sama no Tame ni

Princess Carnephelia was unloved and neglected until she met Helis, her first love. However, under the evil plots of her stepbrother Prince lanfried, she ended up destroying the only boy she ever loved. Devastated by what she had done, the princess swears revenge... even if it entails her life being cursed for eternity. (Source: Pocket Comics) Note: First released in English, with the initial eligible release in Japanese followed by Korean, making it a manga by AniList standards.