The Amorous Son-in-law

My father was a drugger, and he spent all his money feeding his addiction and even amassed a terrifying amount of debt. A few months ago, during another drunken stupor, he wandered off a bridge and fell to his death.
His massive debts were passed on to me. But how could I pay them? I had no choice but to accept an offer which was to get married to a young lady whose family is wealthy.
The day I met the lady to talk about marriage deals, but found that her sister was the girl I saved from hoodlums last night and what's more embarassed is that we had an one night stand in the dark alley that night.