Template:Fight InfoboxLambo vs. Large Ooyama is the third major battle of the Inheritance Ceremony Arc, it features the Lightning, and Mountain Guardians fighting over their pride.
Tsuna and the others decided to camp. While they were asleep, Lambo was awakened by a rabbit in front of him and chased after it and falling into a pitfall. Tsuna and Gokudera also fell to the pitfall and found themselves in a cave surrounded by rocks. In the middle of the cave, Lambo encountered Rauji. Rauji claimed that the dome where Tsuna, Reborn, and Gokudera were trapped held the ceiling up. Lambo still oblivious to the Rauji's intentions tried to get him to play with him. However Rauji refused attacking Lambo in the process causing Lambo to cry and unleash his Dying Will Flames into his Vongola Gear Stone. The stone transformed into Vongola Lightning Helmet Version X but Lambo quickly took it off because it was too tight for him. Rauji then suggests playing sumo wrestlers with only one rule, the person who fall from the platforms loses. Lambo accepted Rauji immediately pushed him of the ledge. Rauji said that if only they were on the same age and if Lambo is not from Vongola, they would've been good friends. However, once the smoke clears up, Adult Lambo is shown clinging to the ledge, saying that now they are about the same age, surprising Rauji.
Tsuna and the others were relieved at this but Adult Lambo told them that because of the hit, he lost his part of his past memory. However, looking around the situation, Lambo realized that it's a one-on-one battle. Rauji then explained to Adult Lambo that this is sumo match and only had one rule: the one who falls from the platform loses. Since the child Lambo didn’t have any pride, he allowed Rauji to create this rule. He also explained about his pride and revealed his Mountain Flame, acknowledging Lambo as his worthy opponent. Lambo decided to fight with his pride on the line and activated his Vongola Gear’s Cambio Forma into huge armor for Lambo, which is heavy for him he fell down.Due to Rauji's mountain flame that allowed him to synchronize with the earth, Lambo was knocked off by Rauji but able to kept his balance from falling. This made Lambo discouraged to fight again, especially after being told that the loser would be imprison at the Vendicare Prison forever, he became less willing to fight and began to cry. However, when Tsuna and Reborn claimed that they regretted their decision for taking Lambo with them because he was still a kid, Lambo stated that they were wrong. In his childhood memories, he was happy to be with Tsuna and the others and wanted to grow up to truly become part of them. He then told Tsuna to always take the younger him with him from now on because he wants to be with him and the others.
Finally remembering how to activate Vongola gear, Lambo charged up his flame and draws the iron sand from the battlefield towards him to form Ellectrico Ironhorn and attack Rauji with Ferro Corno Ellectro Shock. The attack not only destroyed Rauji's mountain, but also Rauji's armor and flames and knocked him out of the ring, thus making Lambo the winner of the battle