Ye Yuyan in that unknown space gathered as many memories that he owns and some that he doesn't. Even some scenes that show the future and involve the Red Poppy Syndicate were collected by him. Some of the mirror fragments were obviously made by the God who called himself Hei Anjing and indirectly helped them for the future where they will once again have to clash with them.
With the special skill, Telepathy, bestowed to them by Hei Anjing. Communication through their thoughts would be a much easier way of exchanging information. Plus, in this life, they are on the same side and both know what is happening in reality. Unlike in their previous world where only Hei Yuhua knows the truth and Ye Yuyan was hidden in the dark. At that time, Ye Yuyan was only an ordinary police officer. If he was working as a hidden agent instead, the government would have allowed Hei Yuhua to ask for his help then all those misunderstandings wouldn't have happened at all.
