Throughout his life and experiences, the Demon King found himself asking three questions.
'Why does the world reject my existence?'
'What is the meaning of my life?'
'Who am I?'
He was born a demon.
A race that needed to conquer planets in order to survive. They didn't really have a choice. In order to survive, demons needed demonic energy, and that could only be created through the conversion of the mana in the air.
That said.
There were only two things that the Demon King remembered about his childhood.
His name.
Jezebeth.
...And the fact that his race was universally hunted down by all the other races in the universe.
Everyone tended to call them a race that held no emotions, but this was far from the truth.