How I am going to explain this is going to be a little weird because I remember pieces of the novel but not the title.

First thing I remember is that the protagonist is a kid maybe reincarnated? But he survives by himself eating demons which is suppose to be poisonous.

Second he trains a party he is with 3 guys 1 girl, the girl has to slay a dragon to save her mother I think?

Third the protagonist destroys a slave market to save a girl that has the same mana as him, he starts to take on the role as her dad.

Fourth one of the fights he uses a skill called gauntlets of immolation or something similar, they almost destroy his arms because the power was too much.

I found out what it is. It was removed on Royalroadl but it is called "The One Who Seeks Power"

https://theonewhoseekspower.wordpress.com/table-of-contents/