Each human mind is a realm
If each human mind is a separate realm, then we can ask what if anything is the connection between a concept in one person's mind and a concept in another person's mind. After all, it seems that shared concepts are a prerequisite for communication. For example, hearing spoken language of no apparent significance isn't enough to allow an infant to acquire language. An infant is spoken to and hears other people speak to each other in contexts involving various kinds of non-verbal interaction.
What was your motivation for choosing the word "realm" in the above excerpt? I see mental functioning as necessarily involving change, an active process. Of course, we might describe somebody as having been "mentally passive" at some time, but I think that is a relative matter. Consider an analogy: running involves an active process, and as bipeds we need an active balancing process merely to stand still, but lying still is inactive and isn't analogous to any mode of mental functioning. Even the unconscious mind dreams.
Each human mind is a realm that contains mental representations of our experiences. The human mind has representations of a circle, circumference and diameter. Our mind also has the ability to mentally rearrange our experiences.
In the above excerpt, does the word "experiences" include not only perceptions, but also conceptions? If thinking is an experience, then the word "experiences" already encompasses the conceptual realm. In that case, it wouldn't make sense to suggest that the mind merely stores and rearranges perceptions.