Lal Mirch and Colonnello are revealed to have a past together where she was the one who trained Colonnello before he became an Arcobaleno. Originally, Lal Mirch was to receive the Blue Pacifier on The Fated Day until Colonnello intervened and left Lal Mirch with a corrupted Pacifier.
When Tsuna fails the test at Mafia Land, he is sent to Colonnello to train for his last-chance test. Colonnello proves he is a vicious tutor and great rival to Reborn by physically attacking Tsuna in a competition to prove who was most strict. After putting Tsuna through the wringer, he falls asleep standing next to Reborn. Later when the two awoke he used his rifle to destroy the Carcassa Famiglia's warships.
He becomes Ryohei's home tutor during the Vongola Ring Conflicts and stays at Ryohei's home. Colonnello was the one to teach Ryohei the Maximum Cannon by shooting him with a bullet specially designed to hold all of Colonnello's knowledge. Later he makes a surprise entrance at Ryohei's match to give him permission to use his full power. He also makes the decision to come to the Mist ring match to confirm his suspicion that Mammon was actually Viper one of the Arcobaleno. He was also an observer during the Sky Match.
Allegedly, during a battle against the Millefiore Famiglia, Colonello and Mammon, already weakened by the Anti Tri-ni-sette Radiation, died. Colonnello had sacrificed him life to buy Mammon time to escape. Unfortunately, Mammon remained trapped, and rather than be captured or killed, committed suicide.
His Arcobaleno Pacifier was sent to Lal after his death. After Tsuna manages to open the Box it was stored in, Lal keeps it until Uni later needed it to revive the dead Arcobaleno.
Colonnello was the first Arcobaleno to administer the first Trial for the Arcobaleno Seals. He fights Tsuna and Gokudera in the Trial of Combat Ability. Gokudera shoots him with various Flame Arrows, but Colonnello was able to avoid them. Colonnello then appeared better than the two, but Colonnello loses to Tsuna's Attack. In the end, Colonnello's Rifle was badly damaged. Meaning, Tsuna won and obtains the Rain Seal and has won the Trial of Combat. He gets captured by Verde, along with all the other Arcobaleno besides Aria, Verde using a variation of non-Tri-ni-sette radiation which only paralyzes the Arcobaleno as opposed to outright killing them.
Colonnello and the rest of the Arcobaleno were called by Reborn to train Tsuna and the other guardians. He was paired with Yamamoto, as they both have Rain-attribute Dying Will Flames. He watched over Yamamoto's training, and noticed that Yamamoto was acting strange. He confronted Yamamoto before his test with Asari about his behaviour and asked if there was something on his mind. Yamamoto responded that due to his easygoing nature, he let everyone down, and he wouldn't make the same mistake again.
During the meeting with Ugetsu Asari, Yamamoto, assuming that the test was a battle, began to fight Asari. Yamamoto was pushed into a corner but notices an opening and tries to take advantage of it. He was nearly successful, but Colonnello intervened and stopped him. Ugetsu Asari then informed Yamamoto that he had failed the test.
Reborn was seen to have a dream about when they became an Arcobaleno. A mysterious man sent Reborn to a certain location where he could meet his new colleagues and he went there and met original "I Prescelti Sette." Suddenly, Reborn returned to his infant form, followed by the rest of the Arcobaleno, excluding Lal Mirch and Luce, who disappeared. Colonnello suddenly appeared in his infant form. The mysterious man then revealed himself. The Arcobaleno showed hatred against him and were prepared to attack him, however, the mysterious man then tells them that despite how strong they were, they cannot use their abilities because they were in a dream. He then makes a proposal to the Arcobaleno, asking if they want to solve the mystery of the rainbow. The man then reveals that the Arcobaleno have to fight amongst themselves with a representative, and whoever is the strongest will be reverted to their adult form. Colonnello expresses his disbelief at this, but later, after the man threatens them with being in their infant body for the rest of their life, agrees to a fight between all Arcobaleno. As a result, Colonnello went to the CEDEF headquarters to request Iemitsu Sawada's help. Later, in his conversation with Iemitsu regarding the request, Colonnello reveals that he's not fighting to free himself from the curse; he wants to remove the curse from Lal, making Iemitsu finally agree to assist him, adding that if it was for Lal, the CEDEF members would whole-heartedly support her.
Later, Colonnello arrives in Japan along with the CEDEF. The day before the Representative Battle of the Rainbow, he trains Basil by firing shots from his gun at Basil, the latter having to dodge them. Later, Colonnello spies on Team Uni and Team Reborn battling against Team Verde. He temporarily releases his curse with the use of his Rainbow wristwatch and notes that he could destroy all of the battlers' wristwatches with his gun in one shot, simultaneously.