On one rainy day, in the city of No. 6, Shion, a 12-year-old boy born and raised in the elite and privileged area of the city, shelters a runaway boy around the same age as him, who introduced himself as Nezumi (lit. “rat, mouse”), and sooner than later departed his home and escaped to parts unknown. Shion’s life was never the same after that day, when his secret meeting was discovered by law enforcement authorities, and on the crime of harbouring a fugitive, he lost everything from his elite status in the high caste of society to his elite home and comfortable livelihood. That sets up events four years later when Shion, on his day at work, would make a shocking discovery of his own that would further challenge his perception of the city workings, and put his life and those of others in grave danger.
