Harry Potter

Narcissa owed a debt to Harry Potter ever since the end of the second wizarding war. She and her family where to be given the Dementor's kiss.

She and Draco were saved from this horrid fate by the boy who lived when he pleaded that they were innocent.

Harry Potter was attending his final year at Hogwarts and she thought she knew the perfect way to repay her debt to the wizarding worlds savior, but he had other ideas.

Or in the savior's words 'Intimate sessions to repay the debt your family has caused the wizarding world by servicing me.'