Maou-sama to Geboku-kun

Kouzaki Seri is caught in a storm one day and gets struck by lightning. Somehow his body is completely unharmed, and he begins to wonder if it was all his imagination. Then the demon king and his messenger appear. It seems the lightning contained the demon king's magical power; without it, the entire demon kingdom will disappear. There may be a way to recover the magic without killing Seri -- but Seri's never been very lucky...