Trying to remember the name of this manga, a fantasy setting where there is apocalyptic destruction (by a black sun?) every so often that a special magic person has to stop. Mc's master sacrifices her life and sends mc to the future where black sun is gone, magic is different, and there's a lookalike of his master or something. I don't think it was very far along when I last saw it a year ago but was hoping to check again...