My Lord the Demon King, Please Don't Lose Me!

[Genderbending, no System, magic, no outline, author making it up as he goes] It's been ten years since I kicked the bucket and ended up in another world. I stopped growing after turning fifteen, and for a hero and demon king, my height is downright embarrassing. On my eighteenth birthday, I picked up a pink-haired elf. The next day, my magic sword turned into a person. Why is my journey in this other world so bizarre?!