Onna Souzokujin ni Kyuukono

When Cassie was very young, both her parents died and left her as the sole heir of a massive fortune. When she grew old enough to marry, numerous suitors lined up to court her in an effort to win her hand and fortune. Viscount Quinlan was one of them. Rumours abound that he has frittered away his own family's fortune through a lavish lifestyle, but Cassie's older cousin, Anthony, who has been her guardian since her parents passed away, told her that Quinlan is trustworthy and invites him to a party. But Cassie wants to find her own fiance and refuses Quinlan's advances, but she finds his kiss too powerful to further resist his charms... (Source: Renta!)