You don't learn it, you have to pick the martial arts choice when you start the game when you are meeting the girls
You can learn it at the beach with the master :)
When?
He is hanging out there 2-3 days a week.
Does he appear even if you have the martial arts skill?
No
If you have a car you can go there and learn it
By the time i am aware of the need fot martial art, its too late to buy a car and wait for summer to reach the master. Got killed by dwayne.
Btw, the hint mentioned martial art is optional, so not sure if the ending is RNG.
How'd he kill you? I have the martial arts skill so I didn't get that part and I'm curious to know.