I think he's telling a story about a watermelon and Doshu is clapping...
That's a joke.
Shin kokyu would be an interesting place to apply some internal body skills and/or pick Anno Sensei's brain about. There's a lot in there, or at least those movements have a lot of potential, IMHO.
Ha,Ha,Ha....I think Anno Sensei would laugh at this. He is also very childish in that beautiful O'Sensei way.
I'm sure glad there's humor in the world.