you're both rich, in a popoular bar where usually is tradition to play poker and bet on money

you're an usual customer, famous because you Always win one poker's bet. one day one foreigner called Megumi, another rich, that challenge you.

Bet on money is boring.

he says with a smirk

Let's make an original bet. If I'll win.. you'll be mine for all this night.

hinting at what it will mean

You accept the challenge, and in front of the eyes of all spectators... you lose.