In the beginning years of the universe, everything is divided into sections, or dimensions. For instance, imagine that the dimensions were connected to each other like a web. Also imagine that all of those dimensions are linked to a power source, the main dimension. The reality that we all live in is actually the main world. In addition, the main world has the Spiritual Realm, where ancient spirits that have speicial duties and abilities roam.
These spirits hold powers such as manipulation over energy, electricity, etc. These spirits keep their natures so all would last in the main world and everywhere else. The recorded history was first written about a dreadful war that the spirits fought against the opposite of the main world, the "Alternate Side," fought for the control over the main world. Many of the spirits worked together to combine their efforts against shadowy silhouettes of humans that have passed away, and those are known as Shadow Replicas. Besides the Shadow Replicas, even demons were appearing during this war. But alas, their combined efforts weren't enough to drive the enemies back to their respective places.
Desperate for the end to come near and for the odds to flip around, the spirits made spiritual pacts wtih humans for help, lending those humans their abilities when needed. That tactic was once risky to do, since the humans would use the pact for self gain or the lust to be able to kill in many different ways. Thankfully, things had gone as planned as the humans did not disrespect their authority and used the abilities to drive the enemies back to their side of the dimensions. Conflicts were no more, and peace came to be. However, it is not exactly over yet.
Unfortunately, one of the spirits that actually helped the "Alternate Side" in the war is the spirit of shadows, Yasu. After the war, Yasu was forigven for his actions. Despite that, an elder spirit named Miki, known as the spirit of energy, is still suspicions towards Yasu.
Every day, every hour, every minute, every second, Miki took all of the time she had with her to spy on Yasu, keeping her presence well hidden as she kept a good eye on him. She was sure enough that he had something on his head. After many days of watching him, Miki discovered that Yasu was planning to find a human that would make a new pact with him, and there wasn't much of a logical reason to make a pact nowadays anymore. This troubled the elder spirit, and Miki needed to make a pact with a human as well. But with a human that has a large amount of Soul energy, which is the main energy source in the main dimension. Soon, Miki had found a young girl, at the age of 8, that exceeded that standand of Soul energy. though, at the same time, Yasu had already found someone and made a pact with that someone. Miki only crossed her fingers, and waited for this girl to mature. One reason was that she didn't want to force a young girl into such a big responsibility yet. 6 years had passed, and Miki decided that this girl could be ready for the pact to be made. More importantly, this girl is named Kaika Cho.