Remember Lambo’s 10-year timeskip bazooka? When Lambo pointed it at himself, he trades places with himself 10 years into the future. Remember now? But what happens if he points it at other people besides himself and Ipin? That’s what this arc is all about.
When young Lambo fires the bazooka on Reborn by mistake…there is no replacement Reborn from the future; Reborn just disappears. When Lambo then fires the bazooka at Tsuna, Tsuna finds himself 9 years and 10 months into the future. He learns quickly that his future self is most likely dead, and the Vongola under his future self is now running for its life!
An aggressive Mafia branch, Millefiore, under Byakuran, is taking control of all the branches one by one. Only the future Vongola branch is large enough to stop him. But even with help from older versions of his guardians, how can the still-whiny 15-year-old present-day Tsuna lead the organization and do that?
To complicate matters, Byakuran is aiming to complete a collection of the Vongola power rings, the Giglio Nero Mare rings, and the Arcobaleno pacifiers. Having them all in one place just may create the ultimate power, one that may let Byakuran rule the whole world.
This is also the arc where rings activate weapon boxes, revealing various powerful weapons including animals.