Four members of Varian, the assassination force under the eleventh generation of Vongola, actually traveled back in time during a mission when the leader of Vongola was still the tenth generation. They want to develop their own stories here.
However, you have to be careful about being fooled by Fake.
Above.
PS: Most of the parts in this article will subvert the original plot, so don't read if you don't like it.