Johnny is a demon-chaser, one of a select group of humans entrusted with keeping the rest of humanity safe from the realms of demons and devils. His partner, Cerise, a half-human, can see the traces of energy, called daemonflash, that mark the presence of an otherworldly creature, even when that creature is hidden from human eyes. Together, they track down the imps, sprites, demons, and occasional devil that attempt to make human lives miserable. Armed with his trusty silver yo-yo and snarky attitude, Johnny’s the one to call when the demons come out to play.