AU where the portal kinda took danny when he died.
So unlike Canon, upon his half death danny got transported to the infinite realms and learned how to ghost over there, rising up in the power hierarchy and eventually at around 20, coming back to the living realm for a bit.
He acts like a full ghost and has no idea how likeley his strength is to hurt people since he trained it arpund ghosts, treating humans like glass and just generally being quite careful with everything else.
Danny decides to Vacay at gotham, due to the ambient ectoplasm in the city and being unable to return to his hometown. He ends up being next door neighbors with one Todd Peters, why by complete coincidence is also undead. They start talking and hit it off.
Jason really doesn't know how to feel about his new neighbor danny, there was something so obviously off about him, too sharp teeth and unwarranted caution when handling anything, even the built to last fridge he'd had installed.
At first the delicate treatment had felt insulting, he was the Red Hood for fuck's sake, he could take a little push! But after a bit it was growing on him. The feeling of being treated with care rather than Brute force, of melting into feather light hugs instead of tanking hits. He started to look forward to it.
So now Danny's worried about hurting the cute revenant next door and Jason's having a crisis over his new not-human neighbor/crush while bemoaning the fact that if any of his brothers found out he'd never live it down.
Also danny not knowing how delicate or sturdy regular people is is so funny to me
Danny, freaking out: shit, is it okay? Will your body.... fix it???
Jason, who just got a papercut: I'm fine.
Or, alternatively:
Danny, covered in blood standing over the joker's mangled corpse: oops, I broke it ):