Tsuna is not quite human, neither are his guardians. Magic and flames can have some odd interactions.

Tsuna and his guardians died in a blaze of glory. Then they woke up, slowly, one at a time, in a different world that was the same in all the ways that really mattered. Or the one where Tsuna and his guardians are reincarnated into the class below the Konoha rookie nine.

Hibari Kyouya travels in time and takes over the world. Basically crack.

Hibari Kyouya travels in time and takes over the world.

Itachi was a good looking troubled teenager left to wander the country unsupervised in the company of a group of insane criminals. He may have made a few questionable decisions involving alcohol and women. It is also worth noting that no-one actually got around to explaining the use of a condom to him. The results are depressingly predictable. Or the one where Itachi missed shinobi sex ed and ended up creating spawn across half the elemental nations, which Sasuke somehow ends up responsible for.

In which all of team seven are poster children for unhealthy relationships with their daemons. Except for Sasuke, who is fully in touch with his inner and outer daemons.

Tsuna is dead. Hayato decides that is Not Acceptable. And proceeds to break space time to fix it. He regrets nothing. Except for the fact that he arrives back in Italy, half a world away from his Sky. He then embarks on the epic mafia road trip from hell to find his Sky, along with three escaped lab experiments, one kidnapped mafia heir, one runaway schoolkid on a field trip to Paris, and a dog called Spot. Or the one where Hayato is incredibly Extra about everything, and no-one but Dino notices.

In which Tsuna has some fairly inconvenient opinions, Iemitsu has been happily living in denial for years, and Reborn now somehow has to sell organised crime to a bunch of student hippie activists. He is not amused.

War Sky Tsuna and Home Sky Kyouya declare war on the Vongola.

In which Sasagawa Kyouko's smile is full of knives, and Tsuna loves her for it.