Please help me look for a manga T.T

[littlered]

Hi, I've read this manga a long time ago and it has been one of my favorites but sadly i forgot its name and i really want to read it again TT^TT. It was set in like a parallel world where there are 2 kinds of people--one who produce energies (or some kind of life-force) and the other who need that energy to live. So they kind of get paired up to help each other survive. The main story is about two boys who were paired up since they were kids, it might be a yaoi or shounen-ai, but there also side stories that aren't. Hope someone can help me find it :3 it was really good and unique