Nobara no Hanayome

From Shoujo Crusade:

Yamada Chizuru was a normal high school student… that is, until her mother left for a “journey” leaving her with a debt of one hundred million yen! As if that wasn’t nerve-racking enough, Kuze Mitsuru, the Umegaki gang’s Sandaime, saves her by buying her to be his fiancee?! What will become of Chizuru’s days?

Contains the side story Coffee is a Black Witch.