(18+) Fgo x Male Reader: Humanity's Last Savior (ON HOLD TEMPORARILY)

Y/N Mayfire was a young teenager from the states who was a pretty solid mage cable of great things. Over the year's he became a special Mage Operative capable of taking down rouge mages and such. However he was on another assignment in Brazil until he got a phone call from the Director of Chaldea calling him for help as a bomb goes off. This is Y/N's story as Humanity's Last Savior.

Trash explanation i know bare with me
Also 18+ because possible 'sauce' and lemon Arc imbound