Jinsei ni Tsukareta Saikyou Majutsushi wa Akiramete Nemuru koto ni shita

Fiona, the most powerful magician in the empire, was tired of being overworked on the battlefield every day, both physically and emotionally. She thought she had given up her life on the battlefield, but when she woke up, she found herself under the protection of Matthias, the most powerful knight in the enemy kingdom! In this powerful and loving fantasy, Fiona recovers her life while receiving love and tenderness for the first time! (Source: Kadokawa, translated)