His world was composed of Angels and Demons, but these realms were always at war because Angels were known as celestial creatures, and Demons as evil creatures. So there was a barrier that separated these two kingdoms

Wally was a demon, and like a normal day he was walking near the barrier, even if it was forbidden he didn't care, until he got close to a waterfall and noticed an angel sitting in the distance, But that angel...Caught Wally's attention somehow..