I call this the “Shun exposition episode.” This episode was all Saki and Shun, for a good reason. Totally loved the BGM for this episode. Surprisingly, I’ve heard no complaints regarding this episode; Yamauchi’s style was perfect for this episode.
We learn a lot of things from this episode. My impression about cantus is that it is supposedly linked to a person’s conscious with the person using cantus to produce a result is basically asserting one’s will through the use of cantus. The subconscious is kept in check by the conscious will. This is the way it should be in Shin Sekai Yori‘s world.
Karma demons are people who cannot control their subconscious and as a direct result their cantus becomes tied to their subconscious instead of their conscious will. The subconscious is a host to many unpredictable things suppressed by the conscious and when the conscious is unable to suppress the subconscious, the cantus becomes tied to the suconscious and unpredictable shit happens. Shun was’t able to control his subconscious and as a result he inadvertently destroyed his village and killed his parents.
Also the Holy Barrier was meant to send the overflowing uncontrolled cantus of the residents of the town to the outside so that it wont affect the residents with the negative karma feedback.
I really like how this episode was a subtle social commentary regarding the Japanese notion for self control. I get that it’s a cultural thing in Japan to assert self control and repress their desire to achieve harmonious balance. I imagine that someone whose desire gets out of control would be a total nightmare for the Japanese.