After tricking Tusha into helping her refine the soul strand she'd left in her, Chun Xu used her knowledge of the mark flashing on the bellies of Xinzi's creampie victims to control the narrative and lead the girls into exile.
First, she convinced A'Zhi, A'Zhu and Yan Le that Xinzi's seed carried demonic properties, properties that would sooner or later turn them into demonesses. That the more the mark flashed, the closer they were to demonization.
The crimson marks brought cultivation benefits so overwhelming that most would liken them to demonic practices. At the same time, the three girls all knew that Xinzi practiced infernal techniques and had already demonized himself. So, they believed Chun Xu, and offered the Dark Chamber of Commerce as a temporary hideout where they could wait for Xinzi to return and handle the situation.