The child from 9999 had a form of madness come upon him due to doing the most unthinkable with time traveling. He wanted to understand consciousness so deeply that he became a consciousness and broke reality doing so. He traveled planet to planet. Universe to universe. Alternate reality to alternate reality. Just to find the reason his world is so disconnected from itself.
Kaguya tells the old foster-parents who found her in a bamboo thicket and have brought her up with lots of love; "I am not a common human being in this world. I am a Moonian. I came down from the Moon as I was destined to. And now it's time for me to return home.My compatriots are coming for me on the night of next Full Moon. I must go with them. I've been in sorrow since last spring to think that you will grieve over my leaving."