Description:

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! (Source: Kodansha, translated)

Alternative Titles:

異世界帰りの大賢者様わそれでもこっそり暮らしているつもりです, The Sage who returned from another world wants to live quietly, Isekaigaeri no Daikenja-sama wa Soredemo Kossori Kurashiteiru Tsumori desu, Isekai Kaeri no Daikenja-sama wa Sore Demo Kossori Kurashite Iru Tsumori desu