Nae Chimdae Mit-e Goemul Namjuga Sanda

Waking up as a character destined to be killed by her family, Irina Sordier refuses to follow the script. She plans to survive by escaping after her father marries her off to Archduke Alexei Ruslan. That is until she is saved from her abusive circumstances by a slime! The two bond quickly, but the slime suddenly vanishes, and Irina laments its loss. Years later, she meets Alexei, but he seems to know things about her that only the slime would! Can Irina save herself and the slime after all?

(Source: Tapas)