Kokuyo Arc: Tsuna's peaceful life is shattered when escaped mafia convicts led by Mukuro Rokudo target Namimori Middle School students. Mukuro seeks to possess Tsuna's body to destroy the mafia world. Driven to the brink, Tsuna enters Hyper Dying Will Mode for the first time using the X-Gloves, defeating Mukuro and earning the rogue illusionist's grudging tie to the family.
Varia Arc: The Varia, Vongola’s elite assassination squad led by IX’s adopted son Xanxus, challenges Tsuna’s group for leadership. A week-long tournament for the seven Vongola Rings ensues. In the final battle, Tsuna defeats Xanxus using the Zero Point Breakthrough: First Edition (freezing Xanxus’s Wrath Flame). Xanxus is rejected by the Sky Ring due to lacking Vongola blood.
Future Arc & Tri-Ni-Set Revelation: Tsuna and his Guardians are transported nearly 10 years into a dystopian future. The Millefiore Famiglia, led by Byakuran, has hunted down the Vongola and killed the Arcobaleno through Non-Trinisette Rays. Byakuran seeks the Tri-Ni-Set (7³)—combining the 7 Vongola Rings, 7 Mare Rings, and 7 Arcobaleno Pacifiers—to acquire godlike power over parallel worlds. Tsuna trains, completes his X-Burner, and gains the blessing of Vongola Primo (Giotto). Uni and Gamma sacrifice themselves to revive the dead Arcobaleno, and Tsuna obliterates Byakuran with his complete Sky Flame.
Series Finale: Upon returning to the past, Reborn asks Tsuna if he is ready to become Vongola Decimo. Tsuna refuses to join the traditional mafia, but Reborn smiles—realizing Tsuna has built his own version of a protective "family".