Fantasy Manifestation

Kuninotokotachi

The flow of energy that permeates all life. While Chakra itself is created by merging Mind and Body energy together, the source of this energy is life itself. And in the same way Chakra can be used to connect individuals through multiple ways, the world itself has its own flow called Kuninotokotachi.

This flow has no real will, but it has an intent of maintain order and sustain life. An inner desire for survival, and it is why all living beings evolve and grow, to keep living. Its power comes from all those who live, and in return it grants them life itself. No creature can be severed from this flow, not even in death, as the Impure World and the Pure World exist simply in this eternal flow of energy.

The Will of the World

Evolution, growth, reproduction, survival, and more. The primal drives and mechanics to which life itself exists and continues to do so are written into the energy flow itself. Whether this was a natural thing or something that was given to this energy flow, it is hard to say.

The second purpose of it is reclamation. Chakra has to be spent to manifest effects that go beyond the mundane, powered by this life energy at its core. And given all life energy is innately part of the Kuninotokotachi, this means that it has to be transitive. The sources of permanent change through techniques are limited, and most of them require re-writing the pyhsical bodies of people.

In the same manner people can reject and fight back against said transformations through their own psyche, their techniques, their bodies themselves; the world rejects transformations to it done through this Will, eventually sanding down unnatural techniques that exist outside its boundaries.

Kuso Genka

A method for which to recognize the existence of the Kuninotokotachi, properly feel its flow, and connect to it.

While hard to find proper use of this on its own, Ciro found two methods to gain direct value from it using his own experiences. The power of a Jinchuriki, by adding an extra source of energy to a body, creating a pseudo-Jinchuriki fueled by the Kuninotokotachi itself; and trying to reach deep enough to influence the powerful energy source itself.

Both of these purposes are highly dangerous and proved to be incomplete for their intended purpose. No body can contain that much energy, and even just fully opening oneself to the flow proved dangerous as there was no limit to how much energy the world seemed to generate. The second problem came that the level of power you need to influence the Kuninotokotachi would inevitable convert you into a mere vessel of its will, or erase your self entirely.

Depth

Depth is a moniker of how much a person can sustain drowning in in the conceptual sea of the Kuninotokotachi without losing their sense of self, or their body starting to reject the immense flow of energy into themselves.

They are broadly separated in three "Stages", but the line can become blurry at times.

Stage 1

A base state when using this ability. The user attains Jinchuriki-like abilities. A large increase in Chakra output and a connection to the Kuninotokotachi, allowing them to use techniques that require said connection.

Stage 2

The advanced state, what most people would consider the complete version of the Technique. Not only the general power boost is greater, but now it allows to create boundaries fueled by the Kuninotokotachi itself, however temporary they might be.

This stage is inaccessible to any current Jinchuriki, due to the energy flow bypassing their seals, and starting to forcefully fuel and unleash the Bijuu inside them. While some might have positive relationships with them, the survival instinct the Kuninotokotachi injects in them overwhelms their minds.

Stage 3

An unnecessary but incredibly powerful state. By now one could be considered something akin to an avatar of the Kuninotokotachi itself. At this stage one is able to permanently alter the rules of the energy flow itself, adding or removing something from the will of the world. However the technique inevitable consumes part of the user, erasing some of their self, and shaving their lifespan.

Trivia

Originally written as lore for a forum before Senjutsu appeared in the Manga (at least in any meaningful capacity), as a way to connect the concept of all living things can possibly carry Chakra, and as a source of where the Bijuu come from. An additional restriction was worked in afterwards, a justification to prevent/restrict "permanent techinques" which was somewhat woven in that I felt had to be kept.
The latter ones are simply manifestations of pure Chakra, created by "the world itself" through its natural flow of creation. They are simply creatures created that exist in this space between the real of energy and the material world, just like how animals, plants or mushrooms exist in their own realms.
And obviously, this also predates the "Everything is Aliens" explanation of the Otsutsuki era of Naruto lore.
Due to most of the original text being long lost, most of this is written from memory, slightly adapted, while keeping the original intents of the story that was being written at the time.