Board Thread:Off Topic / Fun and Games/@comment-38248322-20190311135038/@comment-38248322-20190315012005

Okay. Here's the last but of information that may be actually useful. Please, take a read if you're interested, and again, this work is not my own:

First thing we will be covering is how quirks are manifested, quirks can be inherited genetically and manifest by the age of around 4 years old, this can be much earlier or later depending. Children can either manifest one of their parents Quirks or if both parents quirks are compatible, it can create an entirely new quirk altogether by a fusion of the two previous Quirks.

This new quirk may sometimes give the appearance of someone having two quirks. Such as Shotos Half-Cold Half-Hot quirk but a much more rarely, in the case of (manga spoilers) Eri’s Rewind Quirk, a child may manifest a Quirk that is entirely unrelated from their genetic lineage, this is similar to a mutation.

It is also possible for children to already be born with their Quirks, such as was the case with Present Mic and the very first person to manifest a Quirk, the Luminescent Baby. In other cases it is also possible for animals to possess quirks, such as principal Nezu of UA, although this is a very rare occurrence.

Under Special circumstances, two Quirks may mutate and merge becoming a new Quirk (such as with parents quirks fusing to become a new quirk or One For All), it also is likely that mutations of Mutant Quirks can be inherited even if the quirk itself are not, such as Tokoyami and Koda having appearances unrelated from their quirks, these are most likely genetic mutations from Mutant quirks, owned by their parents or people in their family tree.

There may also be instances where a Quirk doesn't suit the users body or the body cannot handle the Quirks power or what it does. The most obvious example is Izuku Midoriya while he uses One For All for the first time. However some people, such as Yuga Aoyama are naturally born with quirks their bodies can’t handle. Aoyama was naturally born with a Quirk too strong for his body and as such, he needs to war a special belt at all times.

There are several laws and proceeds to ensure the safe use of Quirks, during elementary school children receive Quirk counseling, in order to learn how to use their powers responsibly. Public display of one's Quirk is against the law, except in cases of self-defense, such as when someone is under attack or preventing another from being attacked, this restriction is of course removed if someone has a Hero License.