The Hundred were a literal hundred of GALAX users who were given access to the CROWDS App by Rui Ninomiya. Rui refers to them by numbers (ex. 77) instead of names, but is aware of their identity. When selecting members of the Hundred, Rui only looks for people who will not abuse their power for their own misguided judgment.The Hundred acted several times to mitigate various disasters. Rui dismissed several members who seemed not selfless enough.
In Episode 7, Rui attempted to use CROWDS operated by The Hundred against Berg Katze, but Katze quickly defeats the CROWDS. The Hundred who operated them have been injured, possibly killed, by the feedback.
Later, Berg Katze created his own version of this group, the Neo Hundred.