Shitsuren Maid wa Bikei Gunjin ni Dekiai sareru: Jitsu wa Saikyou Majutsu no Tsukaite deshita

Lilith served the young master of the Gratton family as his maid. She secretly had feelings for him, but after he suddenly got married, his newlywed wife announced that she was fired!! Lilith was sunk in despair, but she found herself getting hired by Dunkirk—the strongest soldier who's good-looking and a womanizer—to be his maid and fake fiancée for six months. Despite that, he treated her tenderly from the bottom of his heart!? On top of that, the power that Lilith held had a secret to it... This is the world's strongest doting love story that begins from heartbreak!

(Source: Kadokawa, translated)