Gal no Ongaeshi

Chizuru has been doing her best for her boyfriend. However, when she ran out of money, her boyfriend dumped her and she collapsed. Just as she was about to lose consciousness, she was saved by an earnest-looking businessman... Chizuru fell in love with the honest businessman at first sight, and in exchange for letting him stay with her, she returns the favor with her body. (Source: KATTS, translated)