I might expand on this at a later date, I'm not sure.
Instead of simply not working when the Fenton couple tried to start up the Ghost Portal, it exploded, causing the deaths of the majority of the adults (25 and older) and children (0 to about 10 years of age) within a couple thousand mile radius of the Fenton house. Danny, Sam, and Tucker were nine years old at the time (the only ones of their year group to survive) and Jazz was twelve. All were there in the lab when it happened.
Now, five years later, Vongola find out that Tsuna had committed suicide in response to the extensive bullying and Nana had followed him in her grief. Iemitsu hadn't known, but he does have a distant civilian cousin, Jackson Fenton, with Vongola blood has two kids and lives in America. So Reborn and a few others are sent to find them in America, only to find a ghost town that isn't really a ghost town.
No one in Vongola had known that the Fenton parent had been killed, nor had anyone known that the explosion that had killed them had released radiation that lead to the civilian government, american mafia groups, and the vindice working together to contain it within the city limits. They had not checked for survivors, so they did not know if there were any.
Reborn, Iemitsu, a newly defrosted Xanxus and his guardians, Basil, Verde, Smoking Bomb Hayato, Shamal, Lal Mirch, and Dino and his guardians are going to be the first search team in the seven years since the explosion to enter the Amity Ghost Zone.
