Is there a manga where a love rival actually steals the MC or sth? :o Any genre is ok~

http://www.mangago.me/read-manga/sabita_yoru_demo_koi_wa_sasayaku/

Shoujo
http://www.mangago.me/read-manga/moe_kare/

Shojo: http://www.mangago.me/read-manga/hirunaka_no_ryuusei/

Vampire Knight is a good one for what you're looking for (you've probably read it since it's popular)