From Chibi Manga

Ex-servant and ex-princess, upheaval love story? Multi millionaire’s daughter Kanna, was very demanding to her servant, Kou. But, someday, her family’s business went bankrupt, and kanna had to live a life which was full of debt…

That time, Kou came back as a giant financial company’s illegitimate son. He was willing to support kanna’s family as long kanna work as his slave…