Kiraboshi Ojousama no Kyuukon

One day, Yoshimi Numamoto is surprised by a girl he's never even seen before...proposing to him! Turns out, she's a sheltered, incredibly wealthy heiress! But while he's dumbfounded at why the highest of high class girls would go after a complete loser like him, she refuses to let up the pressure! Will his high school life ever be the same again?! You won't need an invitation to witness this romantic comedy!

(Source: Kodansha)