Title: My Demon Cry Baby, Maria
Satoru is in mourning. His unrequited love, Jun Mariya, has passed away before Satoru ever got the chance to talk to him, much less confess to him. In the throes of sorrow, Satoru crumples up and marks all over the love letter he had intended to give to Jun someday before throwing it aside. Then, he lies there, expressing his want to die. Out of nowhere, a voice calls out to him, offering to take his life. It is a fluffy little black smoke cloud, claiming to be a demon, having been summoned from Satoru's inadvertent scribbling of a summoning circle.
Satoru is surprised, of course, but intrigued, as the demon offers him a wish in exchange for his life span, which the demon will steadily feed on for the remainder of Satoru's life. Satoru can only think of one wish: to see Jun. The demon takes this opportunity to lure Satoru even further, suddenly shifting into Jun's exact likeness. Satoru is shocked but is more than happy to make this deal so he can be with Jun. Similarly, the demon is delighted to make such an easy deal.
What the innocent demon doesn't realize is that Satoru has some depraved plans for this demonic lookalike, and he has every intention of acting on them until his dying breath.