Tsuna isn't the only available candidate for the position of 10th Vongola boss, but one is even worse than Iemitsu's son and the other shrouded in mysteries (not to mention quite busy with other things). Mysteries that Reborn plans to unravel.
What happens if Harry's luck is not from the Potters, but from his mother, Evans. One world where Reborn has a grandson, a world where Byakuran's primary flame is lightning and a world where Harry unknowingly creates Chaos wherever he goes. "... Congratulations Reborn, he does have the same genetic makeup as you, I swear he's your son, if not because his age doesn't match ..."
He had heard that the Varia had a Cloud Guardian now, but it was only Tsuna's luck that the circumstances around their first meeting was when the Decimo was kidnapped and needed rescuing.
Hariel and Reborn have to share a train compartment and it changes their lives. Ghosts, Cursed Objects, Kidnappings, Shenanigans... Nothing new for them, or well at least for Hariel. Reborn might have some complaints. As do the rest of the people to follow them into madness. Chaos is everywhere. Of course, it is. FEM!Harry Grey!Harry Adult!Reborn.