To My Beloved Master

The eldest son of the Hevonshire family, Lucien, who had been living a reckless life, suddenly finds himself in an arranged marriage due to the wishes of his family. On the eve of his wedding, Lucien, celebrating what he believes to be his last night of freedom, ends up drinking with a mysterious man. Shortly after, he loses control of his body and is taken advantage of.
"I wonder if you have any idea how long I've been waiting for this moment, young master."
Who the hell are you…?