This is a story from Michael Glen of Santa Monica Bujinkan. It was in an email he shared. Here is his blog page to read more from him if you would like: http://bujinkansantamonica.blogspot.com/
The reason I'm sharing his story is because often times we watch Soke and cannot perceive everything he does. Just because we cannot see something, does not mean it isn't real. This happens often with Soke, his movements are so subtle it is almost impossible to always see and understand what he is doing.
"In one class I was training with my friend Yabunaka San. Hatsumi Sensei put a sword in his belt and asked Yabu to try to grab it. Then Hatsumi Sensei drew and turned the blade just enough so that Yabunaka's arm slid across the edge.
If that wasn't bad enough, suddenly Yabunaka yelped and few through the air. It was confusing as an observer. Hatsumi Sensei said "If you don't remember this kind of movement here then these weapons won't come alive."
When Yabunaka returned to train with me, he was rubbing his arm to make the pain stop. He wanted to show me what Soke had done to him. Lucky me... It turns out that after Soke forced Yabu to cut himself on the blade, Soke quickly resheathed his weapon. This had the lovely effect of pinching Yabu's forearm skin between the saya and the blade.
No wonder he yelped! This is why understanding Soke's budo is difficult because you may not see it. You must experience it directly or train with someone who has."
From his Rojodojo email newsletter sent 9/22/2016