Soon we all were sent to Earth

Yuri: "Eventually, we were all taken from our astral forms and sent down to Earth. We were scattered through multiple timelines, appearing where we were suppose to and had any memory of our home erased."

Miku: "Why did they do that?"

Yuri: "Very few demigods are strong enough to carry on without the aid of what they learned. They do this in order to relearn. It's similar to the concept in the Book of Five Rings. To be in a state of nil thought where you forget all distractions and emotions, as if everything you had was second nature. That's all I can tell you about my life in the heavens."