Lullaby of Slumber

When people fall asleep, they generally see dreams.
But when a person's heart is burdened with darkness, it can cause demons to emerge.
Demons which feed off of and taint the hearts of their victims.

This is a story about a young man who is talented at singing and a man with insomnia,
who are members of an organization tasked with slaying such nightmare causing demons.

(Source: DLsite)