
What? I don't get it? Can some kind soul please explain? Thanks.

Basically:
Spirit King or whatever fell in love with his summoner, they lived together and were a couple, she wanted a child so she made a contract with some demons so that they would make her pregnant using the Spirit King's aura (some kind of magic) in exchange for her life.
The Spirit King got grumpy and left her after she formed the contract with the demons, but came back in time to see their child being "born" as she was taken away by the demons, the child was then left on the beach (presumably by him).
I can accept an OP bad guy ML because all game boss monsters are strong ╮( ̄▽ ̄)╭ I cannot accept an OP good guy ML on the other hand. It's just boring. When you play, you got to start at lvl 1