The Highest Debtor

Natsu took a large amount of money as loan from Heartfilia Finance. Threatened by the President, Natsu agreed to a deal to date his daughter till she grows tired of him. He assumed her to be stuck-up rich brat and found the chances of falling for her low. However, his opinion of her changes as the time progresses. He finds her mysterious. What is she hiding? Will he ever find out?