Compared to others, going to John was fairly easy for Lex if he wanted to. John had entered the Origin realm from a planet connected to the Inn. Though he had since traveled away from it, the distance he could have traveled in a short time was limited. Thus, he could always travel to the same planet, and then teleport over whenever he wished.
Since his situation wasn't urgent, however, Lex decided to wait and finish his current endeavors first. The thing Lex was most anticipating was heading over to the Temple of Fasting and learning the Masterless technique that Nuwa had told him to learn. Although he had been avoiding the temple ever since the Humanoid Alliance had probed for it, since Nuwa herself had told him to go there, there was no reason for him to hold back. After all, the temple was her property to begin with.
