Love Quest(2005)

Love Quest

Rejected by the girl of his dreams for some guy named Moriya, Kazunori Akabane is royally ticked off when he unknowingly collides with his rival in the school hallway. Unexpectedly, the accident warps Akabane and Moriya to a magical realm full of wizards, princesses, and monsters! But much to Akabane’s chagrin, the key to the classmates’ survival in this world is…the exchange of their bodily fluids! Can Akabane ever get used to the idea of swapping spit with a guy?!

(Source: Yen Press)

Note: Includes a one-shot and an extra chapter.