- "Don't stare at it. The glow is deadly to the eyes..." - Ginko
It is something visible only to those who are aware of the Mushi world and are able to close their "second eyelid".
Wherever the river of light flows near the surface, nature grows lushly and abundantly, but in places where the river’s flow is deeper underground, nature struggles. Looking directly at the river for too long will cause your eyes to wither and die.
The weaker a Mushi gets, the brighter light it emits; because when a Mushi is weak it is close to its source, the Kouki - which is the basis of all Mushi. The River of Light flows through the Kouki.
In areas where the River of Light flows the strongest, Mushi tend to gather, attracted to the pure life energy it emits. At such places there is always a God in control of that place.