Sword Art Online: Alicization

Kirito awakens back in Underworld, but he does not remember how he got there. He then meets Eugeo, but they have no memories of each other. After helping Eugeo with his daily task of cutting the Demon Tree, Kirito is taken to Eugeo's village, where he discovers that he can actually use his sword skills from back in SAO, and after getting shelter at the local church, he decides that he must learn more about his circumstances before looking for a way to return to the real world. (Source: Wikipedia)