The way he holds the neck, even though the veins are popping out, it doesn't actually look all that tight? I feel like it was the first strike of the technique. That said, secret technique? No. This is a FORBIDDEN TECHNIQUE.
Hohoho.... "Secret Technique" you say. I was only here for the fluff but then you introduce that. I'm now invested more in the series just to know more "secret technique" this guy has.