Metamo Kiss, Volume 3
Kohamaru was born into a family in which you can switch bodies with the person you are destined to be with. His parents can switch bodies, and oddly enough, his aunt can switch with a cat! When Kohamaru literally runs into Nanao, the girl of his dreams, they switch bodies--but Kohamaru discovers that she's in love with someone else. And as if that weren't enough, the someone else turns out to be Kohamaru's twin brother, Konatsu, who has the power to reverse their transformation...with his own kiss.