it's a story about a chemist.. maybe? or mage? I forget. he accidentally drink a potion that made him immortal and after hundreds of years he shut himself in his lab, finally he go out and go to a village, help them wit water issues, then make a girl his disciple then they go to an academy, and help the important figures in the academy in the nearest war with his ancient magic and potions and if I'm not mistaken he has a cat friend or familiar. sorry if it's all over the place i'm not that good with words 
