It wasn't until those two monsters showed up at his doorstep that Zhou Tian had no defenses prepared against their arrival. After all, he had previously assumed that once they joined the organization from outside the Plane, they would become mere thugs for that organization, deprived of their freedom. It never crossed Zhou Tian's mind that they might be able to escape and come after him for revenge.
Due to this misjudgment, Zhou Tian had separated from Bella, because, in his mind, the monsters from the Main Plane really couldn't take him down in the short time before Bella could arrive to help, unless they worked together.
Having confidence in his own strength, Zhou Tian simply did not see the threats from the outside world as a cause for concern, as he believed they could hardly pose any real damage to him.
