A collaboration product has appeared between Yu'er's "City of Kowloon Walled City" trilogy publisher, Creative Palace Co., Ltd., and Hayakawa Publishing's official goods label, HAYAKAWA FACTORY. The folding fan, with a design inspired by the world of Yu'er's "City of Kowloon Walled City" trilogy, is a must-have item for fans of "City of Kowloon Walled City." The fan's background color, ribs, and pivot are in a chic black, with impressive prints in red and matte gold. The engraved "Ryujo" refers to the "Ryujo Gang," which held sway in the underworld from the 1960s to the 1970s, headed by Ryukazen. The black box has a luxurious gold foil stamping, making it perfect for gifts.