The story takes place in a city where it's said that has thousands of levels. In a shutdown area, thousands of levels overlap each other, you couldn't tell the sky from the ground and you couldn't tell which way is up or which way is down. Maybe the original purpose of this story is to unravel the mysteries bound in this time and world. For the humans who found this vast rare multi-level city, the mysterious main character "Kirii" wanders to search for the "Net Terminal Genes" that were not infe (myanimelist.net)