Tsuna is shocked that there are secrets of the Arcobaleno that Reborn is unaware of. Directly after Reborn's declaration that he knows nothing of the Arcobaleno, their Rainbow Wristwatches beep and declare the end of the third day of the Representative Battle of the Rainbow.
Shining his flashlight around, Reborn notices an exit that he and Tsuna pass through. Along the small tunnel, they see multiple murals: all of Checker Face as well as multiple shadowed figures. Reborn reads an inscription on a mural: "The Fated Day". Tsuna is desperately confused, but Reborn explains by telling Tsuna that in the mural, Checker Face had gathered all the current Arcobaleno, and given them several jobs paying a large amount. Naturally, they cleared the jobs without trouble.
Reborn notes that at that time, they weren't doing it for the money at all; it was fun for them to work as a cohesive unit. Eventually, they were given their final mission: to climb a mountain and seek the treasure atop it. However, when they reached the summit, they were bathed in a strange light and cursed. The Arcobaleno fell unconscious, and by the time they awoke, they were all in their cursed infantile forms and had an Arcobaleno Pacifier tied around their neck. Reborn explains that they had previously only communicated with Checker Face via letters, and thus couldn't reach him afterwards. He also explains that Colonnello had took Lal Mirch's place at the last moment and thus became a full Arcobaleno, while Lal had only a bit of light shone on her and became a partial Arcobaleno. Reborn, however, curiously notes that the Representative Battle was also carved on the wall as well.
Jaeger and Bermuda von Veckenschtein walk through the tunnel and explain to Reborn that these murals were in fact left by previous Arcobaleno: their fated days, their Representative Battles. Bermuda comments that it was unexpected that Tsuna would tag along, but nonetheless prepares to tell them the truth and orders them to take of their Rainbow Wristwatches, as Checker Face could listen in through them. Tsuna is initially distrustful of Bermuda, but Bermuda retorts that if he wanted them eliminated, he could have just had his Vindice destroy their wristwatches.
Bermuda and Jaeger then lead them into a room designed to block all electronic waves, but are doubtful of its usefulness, as they were dealing with Checker Face. Bermuda starts by explaining that originally, there were other Arcobaleno, other strongest seven babies. Bermuda explains that the Arcobaleno are strong people Checker Face sacrificed in order to protect the Arcobaleno Pacifiers. Jaeger states that it wasn't a job for just anyone; thus, only the strongest seven of that era would be selected as the seven Arcobaleno. Bermuda then goes on to explain that eventually, the Arcobaleno's bodies would be unable to resist the curse, which would create detrimental side-effects to the Pacifiers. Thus, a passing-on would occur in the form of a Representative Battle, or a contracted job. These passing-ons would be spread wide apart so no one would care to remember them.
Bermuda explains that the Representative Battle was to determine the next generation of Arcobaleno. Jaeger follows up by explaining that the Vindice were in fact what became of Arcobaleno- if they survived the removal of the Pacifiers. Bermuda also reveals that the curse wouldn't be removed; it was just to gather the seven strongest people. Reborn, however, reveals that he had predicted such an outcome, that he would die "a dog's death." Tsuna then asks Bermuda why he participated, to which he replies that he wanted to avenge himself on Checker Face, who was skilled enough to erase all evidence of his existence. Bermuda explains that there was one moment in which Checker Face would be able to be captured: when he was calling the winning team to his side to make them into Arcobaleno. Bermuda asks Reborn for assistance in order to kill Checker Face, which Reborn contemplates.
Note: Bold + Italicized = First Appearance