

The Great Mage Returns After 4000 Year is a Manga in english language, Action series, english chapters have been translated and you can read them here. You are reading chapters on www.thearchmagereturnsafter.com fastest updating comic site.
The Summary is
At the age of 15, Saitou is reincarnated into another world, becomes a great sage, and defeats the Demon King. Immediately afterwards, a door connecting the other world and the real world opens, and Saitou returns to Japan with the power of a great sage. However, 19 years has passed in Japan. Chronologically preserved, Saitou meets his childhood friend, Kanako, who is now a single mother. It seems that there is an enemy who is aiming for Kanako’s life… The slow life wannabe story of a great sage who came back from another world begins!