Vincent meets with Catherine at the Stray Sheep, as promised by Boss. During the meeting, Vincent confesses his love to Catherine, explaining that he is now "free" from the "herd" of society, and makes his proposal to marry her. Catherine is confused by the proposal informing him of the problems of he, a human male, having her, a succubus, as a bride entail ("The whole 'kid' thing would have to be off the table... And I mean, and I mean everything I did to you, I might do to other guys..." ), but Vincent merely suggests that they try taking one day at a time to which she ask if he's okay with that.
However, her answer is cut short by the appearance of Nergal, Catherine's father and lord of the Underworld. Nergal states the a mere human asking to wed his daughter is utterly absurd and states "Not in my house!!". Catherine tells her father to leave because she is having an important conversion. Vincent asks for no more games and her true opinion of, to which Catherine blushes happily and her father asks is she embarrassed over a simple human to which angers Catherine further and causes her to groin kick and tell him to "shut up" to silence him griping.
Catherine then confesses that she does, in human terms, like Vincent and she admits that she supposed to be seducing other human male targets but choose instead to forsake her mission to spend her time with Vincent. This gives Vincent all the proof he needs and asks Catherine to marry him, and with some hesitation, Catherine accepts with a happy "Okay"; they hug joyously while Catherine's father still objects to this claiming that "you're [Vincent] not taking my babyyyyyyyy [Catherine]!".
Several days later, Catherine and Vincent are waking up in his room after a wild night. Vincent notices that Boss is lying in his bed, wearing sheep pajamas. Catherine explains that he is there to watch over the two. She hugs Vincent, saying, "It's better when someone's watching...", and she pulls herself on top of him, and confesses that she really loves him. As she lays herself down on him and they make love, the camera pans out and, through Vincent's bedroom window, the Underworld and Astaroth's tower can be seen, implying that he and Catherine now live in the Underworld.