Fang Yu failed his tribulation while advancing to become a God of Magic and accidentally transmigrated into a Honkai world. From then on, the Honkai world had a new Archmage. People say this mage can set ice pigs ablaze, strike Otto with lightning, and freeze the Heavenly Father!
Kiana: "God, why is there someone who understands space better than I do?"
Fu Hua: "This person's strength is no less than mine."
Theresa: "Don't touch my head. I'll never grow taller."
Rita: "Uncle, your eyes keep staring at my white stockings. Want to touch them?"
Maid Rita: "Lord Fang Yu, shall we play a game tonight?"
Fang Yu: "I can't take it anymore. I don't even have the stamina to fight the Honkai. Who should I teach magic tonight? Hey, hey, hey, Himeko, honey, let me explain. We really were studying magic!"
(PS: Friends who haven't played Honkai Impact 3rd can still read this just fine. The author has only played the Honkai Impact 3rd game and hasn't read much of the manga. If the settings don't match, just consider it a new spin. The original title of this book was The Archmage of the Honkai World.)