The underlying dynamics of the physical world are experienced at varying degrees of consciousness. From the perspective of Ki philosophy; if each aspect of Ishiki exists in potential, the Tsuki equivalent would be the complete understanding of this aspect as it exists in the physical world. For example, if the potential for an entire ocean exists in the plan of Ishiki, the memory of swimming in that ocean would be the domain of Tsuki. For Tsuki exists wherever physical beings create conscious thought and therefore strive to realise the life purpose of Shinki.
It is interesting to note that when we experience the synaesthesia created by our interaction with Reiki, it is Tsuki that symbolises those experiences. We could view this dynamic as a mirror, where Reiki is the reflective surface, Ishiki the source and Tsuki the reflection.
Therefore, Tsuki acts as the reward for everything that has gone before; the ultimate goal of conscious experience and the precursor to a return to Shinki, because Tsuki is also the facet of Ki that recognises itself as Shinki. Tsuki, for all its mysteries and enigma is actually where we lift the veil of illusion and discover ourselves as the Divine. Tsuki is the memory of our oneness and a call home to where the loneliness and separation of the physical world is no more.
This is also where a strange side effect of existence occurs, for when we approach Tsuki, we have had plenty of time to develop an ego-self, through the actions of Kuki, Denki, and Jiki. This ego recognises the illusion of its own existence and fights to deny the reality of oneness—for oneness means losing self-definition and to the ego, this is an absolutely terrifying prospect. What is it like not to be me? What happens when my consciousness is no more? And so on. Hence, it is with Tsuki that both life and death meet in a crucible of experience, both joyous and painful to behold.