[Shield Hero/FGO] My Daily Life as the Sword Hero and the Royal Mage

The full title is Is It a Problem If I'm Summoned by the King as the Sword Hero and Get Up to No Good with the Royal Court Mage? I'm writing this because I'm a huge Merlin fan. The heroine probably isn't the eighteen-year-old star from next door. You can read this as an original even if you haven't read The Rising of the Shield Hero, and you can read it as an original even if you haven't played FGO. Anyway, I borrowed the worldbuilding from Shield Hero to write a romance with Merlin. I started writing this because Merlin appeared in a dream a few days ago, so I'm writing down the scene from the dream.