The Primo Family Arrives! is the 178th episode of the Katekyo Hitman Reborn! anime.
Realizing that Tsuna and his friends need to become stronger before facing Byakuran, Reborn arranges for Spanner to send them, along with Uni, back to the past. As they arrive, the day after they completed the Arcobaleno trials, they are met by the other Arcobaleno, who Reborn has called together to train Tsuna and co. Uni uses her powers to activate Tsuna's Vongola Ring, bringing forth the soul of the first Vongola Boss. He tells Tsuna and his guardians that the Vongola guardians of the first generation will determine whether Tsuna and his guardians deserve to inherit the real power of the Vongola before leaving. Reborn explains that the First's guardians will appear from the ring to test their respective successors. He then assigns Tsuna and his guardians Arcobalenos respective to their elements to train them. That night, the First Guardians appear from the rings of Tsuna's guardians and announce to their respective successors they will be observing their actions henceforth.