While William and his friends ate, he mentioned many of the things he learned about the World in the last few months.
About how Efretta was actually a World created to seal a powerful Cultivator with the same name. About how the Magical Beast Tides were all caused by his attempt to free Efretta, and how he was actually from another World that was created by Efretta.
The only thing that William didn't mention was the appearance of the System and how it was the reason for both his and Efretta's strength. While he trusted his friends, both he and the System felt that it was unnecessary and dangerous to reveal its existence.
For most of his friends, hearing that William was from another World wasn't too eye opening, and Fria already knew everything. Charlotte, however, was different.