The reason why Xiao Hua could cooperate with Zheng Tan and run in the correct direction has to be traced back to when Xiao Hua was still a puppy.
Given that Saint Bernards are naturally large dogs, even as a puppy, Xiao Hua was bigger than other small breeds and, of course, larger than the few cats Zheng Tan had around, but Xiao Hua's temperament was such that it ended up being bullied by the four cats in the courtyard.
From that time on, Zheng Tan started training Xiao Hua. However, to others, it just looked like a cat and dog playing with each other. No one could have guessed that Zheng Tan was actually training the dog. So now, all Zheng Tan had to do was give a gentle tug on Xiao Hua's collar, and Xiao Hua would run in the direction of the tug, or stop if pulled backwards. After a few years, they undoubtedly developed a certain rapport.
Passersby found the combination quite entertaining, though the bloodstains on Xiao Hua were enough to make many of them keep their distance.