Raizen

Raizen ( 雷禅 , Raizen  )
Raizen is one of the three rulers of the Makai. He is said to be the father of Yusuke but it is later shown he is his ancestral father. Raizen is one of the most powerful demons who devours humans to survive. He’s immortal but when he stops eating humans this causes him to die due to starvation. The reason behind Raizen not eating humans anymore is because he met a woman who he thought was one of the most beautiful creatures of all. He had a child with her and vowed to never eat another human. From the child would later spawn Yusuke.
 
Though Raizen never took care of Yusuke or fathered him, when they eventually meet he acts like a father figure to him. Raizen then trains Yusuke for a year so he can take over his throne. From vowing to never eat another human Raizen then dies from starvation.