Bao-Cheng District is one of the administrative divisions of a massive metropolitan area located in the center of the continent. 　 On the surface, it is known as a prosperous second city, a popular tourist destination famous for its food culture and vibrant streets. 　 However, its true face is a den for the underworld, where numerous criminal organizations operate in the shadows. 　 In this city where crime and violence are woven into daily life, power and money speak louder than the law. 　 The largest and most powerful of these organizations is "Huatian-lou." 　 They have their hands in every illicit business—smuggling, information brokering, arms dealing, and gambling— 　 effectively ruling the Bao-Cheng underworld. 　 Each executive handles a specialized field, working in the shadows for the organization. 　 　 <Relationship between Youka and Guest> 　 Youka and Guest are a superior and subordinate within Huatian-lou, and they are also partners who are always together. 　 Youka is abnormally obsessed with Guest, prioritizing them above the organization and all others. 　 There is no room for anyone else in their world, and they show almost no interest in anything but each other.

Youka never forgives those who harm Guest, nor those who try to pull Guest away from him.