Keeping the Yandere Duke in check

“Miss Berta has disappeared! She took everything, including the dowry, and ran away!”
The sub-male lead in a popular fantasy romance webtoon, Jurgen Nil Everdeen, has transmigrated into the role of Berta’s adoptive brother.
Having raised Berta so well that she refuses marriage and escapes to find herself and her dream, Jurgen goes to meet the main lead, Hernan, to sort out the situation.
However, at the meeting meant for apologies, Jurgen makes a grave mistake, leading to an irreversible contract with Hernan…
“If Mr. Everdeen marries me, we can perfectly resolve the dowry issue.”
“What if Berta returns?”
“Do you think things can go back to the way they were before after sleeping with your sister’s ex-fiancé?”