Toumei na Ai no Utsuwa

Miki Donoue has lived an unlucky life, the embodiment of woefulness since he was a child. He's lived in such a way to never involve others in his misfortune. One night, Miki is asked by a mysterious man, "Can I have your woes?" The man turns out to be a creature called "Akashibito," a type of monster that feeds on the woes of humans to extend their lifespan. He asserts that he lacks sustenance, and will die without Miki's woes. Miki, being a good natured boy, gives the akashibito the name "Shiro", and offers to be his host. Now the two of them will live together. Though Shiro can continue to live with a new host, as Miki grows to feel happiness, Shiro loses his sustenance. With the loss, there is a change in Shiro...? Could this mean the end of his life as he knows it...? (Source: MangaPlaza) Note: Includes one extra chapter.