Looking for certain yaoi

I'm looking for a yaoi I read a years ago.

The main use was in the human world and a couple of seconds before he was killed (I think by a vehicle) a supernatural snake in another world brought him to his world. Now the snake is a almost a God but needs to spends his whole body with his fated partner in order to become a God aka a dragon. The person he saved was his fated partner but he ended sending him back to the human world.

If I remember the yaoi was in black n white