A Lovely Lonely Land

A Lovely Lonely Land summary:

Ai is a middle school boy surrounded by mysteries. It's almost impossible to harm him, for one. Then there's a girl that appears next to him when he sleeps, a girl who doesn't breathe. Finally, there's a portal in an alley in his town that only he can see. One day he enters that portal and finds himself transported to a whimsical world that holds the answers to his mysteries.