Yuukyuu no Gusha Asley no, Kenja no Susume

Two millennia of isolation would break most people, but Asley is no ordinary young man: an ageless and reliably foolish sorcerer, he has spent those centuries with only his Level 100 dog Pochi for company. When the familiar insists he step outside for the first time in two hundred years, Asley resolves to rejoin society, put his magic to the test, and shed a collection of embarrassing titles attached to his name. The wider world offers fresh adventures, evil worth fighting, and the odd chance to help Pochi win the mysterious Familiar Feud. Whether he grows up or flees in disgrace depends partly on how well he tolerates his familiar's blunt advice.