The self is an illusion, a sense of a provisional or imagined self, and when that disappears, the true consciousness exists (therefore, it is "existence" or "color"), and that is emptiness. The disappearance of the self is "emptiness," but even when the self disappears, "existence" or "color" remains, and the overall flow that includes these is expressed as "emptiness."

The concept of emptiness seems to be referred to by different stages by different people. Ultimately, emptiness is limitless consciousness, so it is "limitless" in the literal sense, and therefore it is not something that is restricted by the concepts of words or the perceptions of people. It is empty because it is infinite, but people often try to confine the concept of "emptiness" within the limits of their own understanding. That "limitation" is also a manifestation of the ego. For that reason, the interpretation of what is emptiness varies from person to person. Ultimately, it can be said that because it is infinite, it is something that cannot be grasped by human perception, and therefore it can only be expressed as "understanding." Reaching the true "infinity" is practically impossible within the short span of human life, so a certain degree of "emptiness" becomes the destination. Therefore, even if one glimpses the vast expanse of the ultimate universe, it is not truly becoming one with the entire universe. Even if one feels that way as a perception, it is like a river flowing into the sea, where the sea and the water become one. Even if the consciousness does not truly expand to the entire universe, one can feel a sense of oneness, a certain degree of expansion of perception, and a certain feeling of the universe. And that is enough. Knowing a certain degree of oneness and leaving the ultimate aspects to be understood as "understanding" is the story.

Because so few people reach that level, there are times when even the stage just before the true stage of emptiness is called "emptiness." The depth of this stage of "emptiness" is an endless story, a story with no destination, a story that can go on forever. Therefore, while there is a concept of "emptiness" as a temporary goal, it is better to think that there is something ultimate beyond that. With that premise, there is no need to embellish the story of "emptiness" with mysticism. Originally, "emptiness" is infinite, but in the world, it is almost always an intermediate state.

The essence, while appearing to be "existence" (or color), differs from the "existence" of infinity and the apparent "existence" of matter in the phenomenal world. Everything is full, so it exists, but the "existence" visible in this material world is a "semblance of existence," which is not eternal. From the perspective of mental recognition, there is a state of "nothingness" or "emptiness," and beyond that, there is "existence," but this is "existence" as infinity. Initially, in ordinary conscious recognition, it is "existence," but the "existence" in the final stage, although seemingly similar, is something different. It can be said that it is actually the same thing, but it is easier to understand if it is treated as different for the time being. Because this world is one, everything is the same, but in terms of the stage of recognition, the initial "existence" and the final "existence" are different.

・The ordinary "existence" of the conscious mind. Material recognition in the phenomenal world. Mistaking the "semblance of existence," which is not eternal, as "existence." In yoga, this is the world of Maya.
・"Nothingness" from the perspective of the disappearance of the self, or the temporary cessation of the self, which is a temporary cessation of the self accompanying the temporary cessation of the mind.
・An intermediate state. Cognitively, it feels like "nothingness," but also feels like "existence" (which is also the final "existence"). A vague, ambiguous state, which is called "emptiness" (some people call this "the realm of demons").
・Recognition of complete "existence," or some people call this "emptiness." The stage of recognizing the "consciousness" that exists deep within the mind. This is also called Samadhi.

In Japan, due to the understanding of Buddhism or the Heart Sutra, the concepts of "existence," "nothingness," and "color" (form, matter) are often confusing. It is easier to understand if you interpret it from a yogic perspective and then interpret it in accordance with Buddhism and the Heart Sutra.

・The world of Maya. A world that is not eternal. This is the ordinary "existence" that the conscious mind recognizes, but it is not true "existence" because it is an illusion (it has a beginning and an end, and is not eternal).
・The temporary self, the eternal self, the self that is an illusion (Jiva). Due to the illusion, "existence" and "nothingness" are recognized.
・The true self (Atman). This is the infinite and eternally existing "(true) existence." The self as an individual. This corresponds to "emptiness."
・The totality (Brahman). The self as a whole. This corresponds to "emptiness."

When considering this framework, it is possible to understand the story of "emptiness is form" in the Heart Sutra. However, this is not literally the same thing. In this framework, Brahman, which corresponds to the totality, is literally everything, so everything in this world is Brahman. Therefore, even if the Heart Sutra expresses it as "emptiness is the same as form (matter)," it is not wrong.