Could there be such a coincidence? In a certain cycle, it just so happened that none of the nine of them heard the "echo," so they all lost their memories at the same time.
Furthermore, the other "participants" that the nine had known also happened to not have the "echo," so no matter what they did here, it would be difficult to run into an acquaintance. The possibility of this situation occurring certainly existed, but the probability was very low.
"The infinite monkey theorem," Qi Xia murmured to himself.
If you let an infinite number of monkeys, spending an infinite amount of time, randomly type letters on a keyboard, then one of them will certainly be able to, one day, continuously and accurately type out all the works of Shakespeare. Although the probability is infinitely low, it is something that can happen.
Qi Xia was in such a situation right now. If they went through enough cycles, then at some point, with an extremely small probability, a situation of "total amnesia" would occur. This would make them think they had just arrived here.