The main character has everyone he care about followed by one of his shadow soldiers without them knowing. He does it with good intentions but there is at least one scene where he looks through the shadows eyes and accidentally sees a woman hlin the bathtub. No nudety is shown and he is embarrassed about it but doesn't tell her.
The main character has the power to reawaken monsters as part of his shadow army once they are defeated. Some of them are shown to retain the memories from before. It's not really ghosts per se but it is called necromancer power and they appear kind of shadowy ghost like transparent at times.
In addition to people falling unconscious because of fighting there is an illness that makes people fall asleep in intervals that become shorter until they sleep forever. Only two people are healed from it in the main timeline but they are the only two shown wth the illness.
Episode 2 - the healer spits out blood when she heals Sung and then Sung vomits blood two times during his battle
Episode 3 - when Sung returns from his penalty training he is sick. No visual but audio. Last a few seconds only.