Zero spent the rest of his days going through the Dark Guild website and the chat history of Jester. He is working on getting as much important information as possible.
He was also trying to see how Jester's relationship with other members of the Dark Guild was. He had to know who his friends and enemies were in order to act like Jester. However, honestly, judging by the fact that he didn't have any friends on his social media or happy chat with other members of the Dark Guild, it showed how his social life is.
Connecting this with the fact that he was also sent to a remote place to work meant he was a lonely person or an introvert who got bullied by others. This also worked in favor of Zero as he could not be easily identified as suspicious if there were not many people who knew Jester.