Yuukyuu no Gusha Asley no, Kenja no Susume

When he was young, he had failed at the Magic Academy

and was looked down by others.
However by chance, he discovered a mythological medicine, so he obtained an immortal body.
In order to get revenge on the people who made fun of him, he began researching magic and magical artifacts different from the academy. After 5000 years of research, he has become an ancient magic user before he noticed.
The people he was seeking revenge were long gone, losing his purpose, Asley went on a journey to see the world after 5000 years with his familiar Pochi.
With an unexpected turn of events after helping many humans, he is now living at the magic academy.
A 5000 year old man with a young appearance Asley, how will he live his second life’s youth?