I need you (Gratsu fanfic)

Natsu is a mighty dragon slayer that's conquered many foes in the past. So when Natsu went on a solo job with happy, nobody questioned it or was concerned. Until a week later when nobody showed back up.....

(This is after the Alvarez arc. But as I don't know what's going to happen in 100 year quest, That's where we're drifting into our own thing.)