Summary
There was a mage called The Lone Demon King at the frontier
He was just a creature that never grew old but he was loved by the villagers as something of a guardian deity
However he was destroyed by a magic organization that sees his existence as dangerous
200 years later he is reincarnated as the second son of an aristocrat and obtains the strongest magic power
Lets pretend to be a human this time
However being a human lover he didnt particularly think of revenge and has decided to pretend to be human in this life
In his past life he was the guardian deity of a region and in this life hes a local aristocrat but he does not know common sense He doesnt know how to take it easy
As the second son of an aristocrat he is loved by his family and friends and while he is regarded as a master of magic in the magic guild he becomes an Immortal Mage behind the scenes