Izuku has a healing quirk and is stain's cousin or little brother au
Izuku's quirk is called healing fluids, abd as you can tell he can pretty much heal with his fluids
Izuku's saliva can be used as an anesthetic/anesthesia
If someone gets like a cut or somethin then izuku can lick it and it will become numb under 1 min
But if izuku get's the person to digest his saliva like through a kiss then the target will end up going to sleep
As for healing he has to use his blood
Depending on how much blood he uses or the blood type it can either slow down the process or make it faster
Like if a person has type B blood then they'll take the longest ranging from 10 too 15 min to even 20 depending on how much blood they're giving
If a person digests a cup of blood then they can regrow a limb but they will undergo pain that can make a person feel like they're being burned alive or being stabbed to death
That is where izuku's saliva comes in, say if izuku was regrowing someone's limb he would first make them drink his blood and then have then digest his saliva so they won't have to go through the pain but they will feel incredibly weak and will need help doing anything for a couple of day's or even weeks
But ye that's all i haven't thought about drawbacks yet so y'all can just think of what ever tbh I've had this au in mine for a good couple of months or so but ye