So, finally managed to learn this. The only thing that might have been a character flag that changed was I noticed when using the Matsuo finale that I got the "Man, this has got to be the best way to watch anything. You're not sure if you should be sad it's illegal or relieved." message.
I went through about half of my energy of the effect before moving to the charnel house reopened, thinking maybe fight demons would help. Still nothing in particular, but then when I added Power Strike to my deck, the first time I ended a combat after having used that, I learned the tech.
With 5 energy of the effect remaining, I learned two more instances. One in a fight where the only thing I did was a Parry/Demonslaying Blade/Leaping Dodge chain. Added each instance to my active deck as I learned it, and kept Parry/Swordplay/Power Strike/Leaping Dodge active as well.