Yamamoto enters the battle after saving his friend, Kaoru Mizuno to fight against Demon Spade. Kaoru cries still thinking he should not have been saved by Yamamoto because of how he injured him. Tsuna and Demon wonder how Yamamoto had healed from his wounds. Demon says that he should've been in 'critical condition' and could not have healed this quickly to which Yamamoto replies saying that Demon should have died long ago. Demon still wonders how Yamamoto was saved and he says that he was saved by an old acquaintance of his, Tsuna and Gokudera stare in surprise to the old acquaintance part. Demon becomes enraged saying that his plan has gone for the worst and wants to finish it by his own hand like he did before.
Yamamoto becomes excited because he hasn't been in a fight for a while and Hibari gets mad because Demon is his prey. Gokudera and Tsuna become worried because Yamamoto does not have his Vongola Gear to fight against Demon Spade, but Yamamoto tells his friends that he brought it with him and reveals his Vongola Gear, the Necklace of the Rain Version X. Tsuna and Gokudera are surprised, saying that it got an upgrade. Yamamoto calls out his two pets Cane di Pioggia ver. Vongola and Kojirou and turns them into Cambio Form, turning his outfit turns into the one that Ugetsu Asari wore (excluding the hat), holding two swords. Tsuna calls it the 'Two Sword Style Vongola Gear'. Demon stares in amusement at him, then attacks Yamamoto. Yamamoto blocks with great speed with both arms protecting himself from Demon Spade's scythe. Demon forewarned Yamamoto to not just watch his front as another weapon comes from the ground about to stab Yamamoto. Gokudera screams for him to look behind him when Kaoru blocks the attack with his own body. Kaoru says that Yamamoto could have blocked that attack but tells him that he must repay his debt to Yamamoto. The Vindice come in saying the loser was Kaoru Mizuno. Adelheid Suzuki tries to defend Kaoru, saying that he had not figured out his pride yet but the Vindice say that his pride has already been broken. Kaoru says that his pride was in the Simon but he felt like he was betraying all his friend that were kind to him and that he wanted atone for his crimes, losing his capability to fight the Vongola. Demon then interjects saying that Kaoru was a piece of junk and says that they can now watch an interesting show. The Vindice then reveal the fifth 'key' that was a torn paper with a Dying Will Flame. Demon says that the next memory is of when Simon Cozzato was killed.
In the memory, Demon was talking to hooded figures who said they had found Cozzato and that he was holding his own against the enemies. Demon says that he will come to Cozzato's rescue bearing the document of Primo's sign of approval letting down Cozzato's guard. He then goes to Primo who was waiting for news of Cozzato and Daemon, who is wounded very badly, says that it’s to late for Primo to save Cozzato. Primo looks down in shame, saying to Demon that he was indebted to him, Demon smiling in victory. Then the hooded figures that Demon was taking to earlier come into the battle saying they are reinforcements for Cozzato and he replies saying that they are lying about wanting to help him but to kill him under Demon Spade's orders. Cozzato tells them that he knew that there was a traitor among the Vongola because the third letter he got from Primo was a fake; he knew because Giotto signed his letters with "Giotto", not "Primo". Cozzato tried to act fast but noted that Demon was already one step ahead of him but says that he would fight to the end for his Famiglia. The hooded men tear the paper in two saying that their boss was one step ahead of Demon Spade and take off their hoods to reveal the Vongola Guardians. They then say that they would defend Primo's and Cozzato's friendship to the end.
*Note: Bold + Italicized = First Appearance