Yume no Kyuukonsha

Three years ago, Emma was engaged to a wealthy nobleman, but it ended in disaster. Now Emma is planning to marry off Amy, her younger sister, and then she can become a governess. However, Amy is being pestered by Charles Hawthorne, a well-known prodigal aristocrat! Emma finds herself drawn to the man’s charms but is shocked when he and her brother engage in a duel. When Emma begs him to stop, Charles tells her that in return she must become his lover! Source: Harlequin