The following contains spoilers for Yurei Deco Episode 4, "The Yurei Detective Club," now streaming on Crunchyroll.
Four months have passed since the explosion of Berry and Hack's great escape; predictably, the two have faked their deaths so the authorities aren't chasing after them anymore. What's strange then is that Episode 4 of Yurei Deco immediately dives into new developments, with Berry seemingly unfazed at the fact that she's basically on the run now. She doesn't even seem all that concerned that her parents are mourning her death back at home.
Perhaps this shift can be explained by the story's change of location. Because Berry is now a yurei -- an unregistered citizen, although her Deco still sort of works -- she now lives with Hack and the other yurei on the island's outskirts. The look is distinctively different from when Berry was still using her Deco. This might seem like another adventure -- until she returns home for a case and realizes just how big of an impact her 'death' has had.
Berry and Hack can't live life on the run forever in Yurei Deco; the detective club will have to get to the bottom of the Zero Phenomenon mystery if they want to clear both of their names. But first, they'll have to look into the backend of the data to see what has been falsified and deleted to cover up the Zero Phenomenon. They can then work backwards and figure out who the real culprit of the Zero Phenomenon is.
The detective club is really there for the purpose of the Zero Phenomenon, but it attracts their first client, Mitsumame, who is searching for his avatar which is the appearance of a young girl. What makes this case intriguing is that his avatar went missing at the time of the Zero Phenomenon. Berry immediately volunteers to take up the case.
Berry starts her investigation by hacking into her parents' workplace. She eventually finds Mitsumame's avatar in the discarded folder but only has a few seconds to grab it before her parents unexpectedly log in -- in the middle of the night. It's one of the more poignant scenes in Episode 4. Berry's parents are grieving over the 'death' of their daughter and because it's sad, Berry's data will eventually be wiped from the system and she'll cease to exist. It might even be her parents' jobs to discard her data.
Being a yurei has opened up Berry's world by allowing her to actually be able to touch things, meaning she's more grounded in reality. However, this also means she'll be seeing sad things and bad things -- details that the authorities like her parents have actively tried to prevent the citizens from seeing. Eventually these systems will wipe the data they deem 'bad' or 'unnecessary' from people's memories. It's the same with yurei -- sooner or later, those who remembered them before they were yurei will soon forget they ever existed. They become zero.
Despite Berry hardly looking fazed by her predicament in Yurei Deco, these four months have evidently taken a toll on her. Finn guesses the case of the missing avatar may have resonated with her since she's also a missing child -- which is part of it, but the other part is the frustration.
Now that Berry has seen the world, she's angry that the authorities have taken this chance to see more than the self-constructed virtual reality from people. The answer to the Zero Phenomenon may lie in the secret backup system that the city has that contains all the data -- including the uncensored parts.