Shift

is a Japanese light novel series written by Hisamitsu Ueo, with illustrations by STS. The series began publication on June 10, 2008 by ASCII Media Works under their Dengeki Bunko publishing imprint.

Synopsis
A mysterious phenomenon that happened among some young people-when you sleep, you "shift" to a fantasy world similar to an RPG (role-playing game), where you live another life. I don't know why this happens. The only hint was the words "the world is waiting for clearing" that you hear when you "shift" ... "Real world" and "shift world", depicting the daily life and adventures of boys and girls who go back and forth between the two worlds every time they sleep.