With how much time everyone had on their hands and how much of it they spent on training their mana, it wasn't strange that some of the island's inhabitants showed signs of progress. And the first one to show signs of reaching the next level was Lucy, despite being the one who played around and slacked off the most.
Breaking through to the fifth level from the fourth wasn't as drastic a breakthrough as one from the third to the fourth. And it doesn't require any changes in the mana. The only thing Lucy needs to do to complete his breakthrough is compress his mana and expand his mana pool, sort of like a continuation of his previous breakthrough.
Lucy finished his otherwise rather discreet breakthrough with flair as he enveloped all of his spectators in a cloud of darkness that dissipated shortly afterward.
