Kawaii Ore no Oyome-san

Ryusei is a rich heir who lives a carefree life as a flirtatious playboy. One day, he is suddenly propositioned by a plain-looking office lady he doesn't recognize. She turns out to be the secretary for his father, the company president, and she seems to be gunning for a political marriage with Ryusei...? (Source: Vanilove, translated)