Nisekon - Danna Koyou Keikaku
From ShoujoHearts:
On the same day her cheating ex-boyfriend gets married, Rie wins 1M yen in the lottery. She meets a cameraman, Yuu, at the ceremony and makes a desperate promise to "hire him as her husband". Fooling around, registering their marriage, creating an "employment contract"...where will it all lead?