>>56611052I can't remember the source where I read this and might be hallucinating but I recall reading that in Japanese antiquity before the importation of Buddhism brought Chinese anatomical texts, the kokoro ("heart") was once described as being an organ located in the stomach and being long and rope-like in appearance. Like guts, basically, or maybe part of the umbilical cord. The kokoro's function is connection. I believe the Red Chain is a symbolic representation of this ancient idea of kokoro which Cyrus wields as a weapon to control others until it breaks.
Assuming the source I'm thinking of exists, of course. As you said, the red chain as a metaphor for a means to force empathy and connection stands on its own without any mythological basis.