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Team Fon & Dino vs. Team Mammon is a battle occurring on the second day of the Representative Battle of the Rainbow that pit Team Fon and Dino against Team Mammon, which took place at Team Mammon and Dino's hotel.
Team Fon and Team Mammon face off in their hotel, with Mammon thinking that they couldn't lose after coming to the second day, and with Fon thinking that it would be a little difficult for Hibari to face Team Mammon.
The beginning of the battle starts with Fon releasing his cursed form and easily defeating Team Mammon's three members Levi A Than, Lussuria, and Belphegor. Squalo is invigorated by the challenge Fon presents, but Hibari is displeased with Fon interfering with battle. Fon reasons with Hibari, stating that he couldn't leave Hibari to such a great danger by himself. Hibari, however, pushes Fon out of the way and tells him that he could handle Squalo on his own. Squalo, however, stops Hibari and states that he wanted to fight Fon. Suddenly, mochi is spit into Squalo's face by Xanxus, who was taken to the battle by Mammon.
They exchange a few words before they begin the battle, and immediately all combatants fight in a blurry whirlwind. The combined attacks of all four break the hotel's top floor's windows, but Fon is the only one to emerge scathed. Fon dismisses it, stating that he was unused to his new body, but uses a move that he claims can allow him to move and react in microseconds. He then uses his fighting style, Exploding Gale Fist. In response, the other fighters unleash their Box Weapons. Fon charges at Xanxus and Squalo and uses Exploding Dragon Fire Dance, eliminating Squalo and nearly eliminating Xanxus. However, Fon hears a strange sound and falls to the ground, his entire body covered in lacerations. Mammon drops down from the ceiling and confirms Fon's statement of his move, Viper Mirage R, and announces that the special rule he set for the battle was that anyone that doubted in their victory would be eliminated.
Fon fights Mammon while Hibari fights Xanxus. Mammon takes Fon into an illusionary world within his mind, while Hibari and Xanxus clash and fight on an even level. In the illusionary world, Mammon paralyzes Fon and prepares to deal him a devastating blow, but Fon easily breaks out of the paralysis and defeats Mammon's strongest illusion, Uroboros, with ease. Mammon, doubting in his victory, begins to self-destruct, but Fon tries to stop Mammon's thoughts by knocking him unconscious. However, he then turns back into his cursed form and is thus excluded from battle. Mammon is triumphant, while Fon is despairing and begins to self-destruct, and Mammon and Xanxus begin a joint attack on Hibari, with Mammon freezing Hibari with an illusion and forcing him to hold his arms out. Xanxus charges up a shot from his X-Guns and fires, but Dino saves Hibari in the nick of time by pulling Mammon's arm with his bullwhip, stopping the illusion and freeing Hibari, and tells Mammon and Xanxus not to lay another finger on his pupil.
Hibari questions Dino why he came here, to which Dino replies that he merely came at the will of Reborn. Dino reveals that Reborn had told him to take Hibari's side if he was losing, as it would be troublesome if he lost. Mammon still puts up a confident face and announces that it didn't matter who came to fight them; he and Xanxus would destroy them all. Xanxus, however, tells Mammon to stand down, as he was heavily injured. Mammon protests, but Belphegor tells Mammon that Xanxus just wanted to fight alone. Mammon desists and reverts to his cursed form.
Dino, with a mischievous expression, calls out to Xanxus that he had vastly overestimated his abilities, as he had already lost to Tsuna. Xanxus immediately flies into a rage, much to the shock from Team Mammon, and Dino notes that his fury had made his old injuries surface. Xanxus angrily releases his Armatura di Platino Ligre Tempesta di Cieli, following up with his Cambio Forma with new Varia Ring into Pistola Imperatore Animale, then destroying the spiked balls Hibari's Porcospino Nuvola ver. Vongola sent at him instantly. Xanxus charges up another shot, and Squalo notes warningly that Xanxus's shot would destroy the entire floor. Belphegor quickly jumps out of the window with the unconscious Levi A Than and Lussuria in response.
Dino quickly appears beside Hibari and tells him that Xanxus's Boss Watch could be destroyed in the slightest of openings, and that his Vongola Gear would be the weapon to do so. Hibari holds his left tonfa loosely, with the chain hanging out. Xanxus fires his shot, and Hibari charges and strikes down with his tonfa's chain, but a huge explosion blows up the entire top floor of the building. Both Hibari and Xanxus emerge, still in the battle, but their Rainbow Wristwatches announce the ending of the second day of battle.
Hibari is enraged by the restriction of fighting Xanxus, and thus breaks his boss watch, rebelliously announcing that he fought when he wanted to. Xanxus agrees and prepares to do so as well, but his eliminated teammates jump on him and prevent him from doing so.