Read I'll Do That Marriage Manga:
Lilian McKellion, the girl who wanted to avoid a bad end, willingly went to the insomniac emperor in place of her sister, Laelin.
She is tasked to help the sleepless emperor, who was cursed by a witch, by using her ability to induce sleep whenever she touches another person's body with her lips.
Can Lilianne survive being with the emperor, ‘Kael Rue Kaldorf?'