Original Webtoon :
Ridibooks

Anna, a dimension traveler, enters the ominously nicknamed “Swan’s Grave”—the Loengrin Marquisate—as a maid, in hopes of finding a way back to her original world. There, she encounters Marquis Rothbart, who mistakes her for his long-lost wife and forcefully claims her. Soon after, he makes a shocking proposal: “Become my wife’s replacement.” He also reveals the only way for Anna to return to her world: she must bear a child with someone from this world. As she hesitates, Rothbart’s son, Svanhild, also lingers by her side, pleading: “I want a mother, Anna.” A relationship doomed from the start. A condition she cannot refuse. Desperate to return home, Anna accepts Rothbart’s proposal…