The Grand Duke Has Awakened in a Strange Place

"Pretend to be the young lady and maintain the engagement for just three months."

I got thrown into an R-rated reverse harem novel and possessed a side character, only to watch the female lead die right in front of me. To make matters worse, her family demanded that a commoner like me impersonate a noble lady. I was ready to refuse without a second thought, but—

"Once the contract is completed, you'll be paid five million in full."

It was enough money to live comfortably for the rest of my life. My debt-ridden commoner's body reacted faster than my mind.