Large, along with the other Simon Members, except for Julie Kato, watches Adelheid Suzuki and Kyoya Hibari fight on the rooftop of the Namimori Middle School and says that Adelheid got her self into some trouble. He was fairly surprised that Hibari was able to push Adelheid across the rooftop. But fortunately, Reborn was able to stop the fight by pushing Tsuna between the two. Reborn says that the Simon are the Vongola's guests for the Inheritance Ceremony, Reborn even states that the Simon Famiglia has been their ally even before the time of Primo, but he did not know of them because they have become weaker over the generations. Which shocks everyone one of Tsuna guardians. Adelheid, however, responds that they will attend school normally, without any interference. After Gokudera heard that Tsuna was attack by a hitman, he calls a meeting between the two families. Large is seen with other Simon Famiglia members expect for Julie, Shitt P!, whom Adelheid says is meditating and Vongola Guardians in a restaurant, discussing about how to protect Tsuna during when the Ceremony comes in way. But before arrangements could be made, Adelheid says that they need to discuss this with the other members, who are not here.
At the Simon Famiglia hideout, Adelheid proposes protecting the Vongola Famiglia, but in their own way. Everyone agrees with the idea, Adelheid also asks everyone "has any one taking good care of "that"?", in which Large and everyone else responds as a yes. She then asked Enma to show them the Ring that proves that he has the inheritance to be the Boss of the Simon Famiglia. The Simon Famiglia later told Tsuna that they will guard him while eating breakfast at his house along with Large and Kouyou Aoba. Each of them will stay in his house to guard him, with the first day being Kouyou's turn. Lambo who has already taken a liking towards Large, is grouped with Lambo to patrol Namimori Park to protect Tsuna. Later, to Tsuna's surprise, Large casually agrees to work under Lambo. He and the rest of the Simon Famiglia are seen at the at the hospital with the others about Yamamoto's condition after he was attacked in the baseball locker room by Kaoru Mizuno. Kouyou also tells them that they no had leads, but was interrupted by Reborn, who said that he had found a lead. This news surprised the Simon Famiglia, but Reborn said that he couldn't share it with the Simon Famiglia since it involved "secret information about the Vongola." The next day he is seen at the Vongola Inheritance Ceremony with the rest of the Famiglia. Large and the rest of the Simon were all surprise to see Takeshi Yamamoto heal from his wounds, but they didn't say anything about it. He is later seen amongst the crowds during the ceremony waiting along with the rest of the Simon Famiglia, when Tsuna was to receive the Vongola Sin from the Ninth. But before the Ninth could have gave Sin to Tsuna, an explosion is heard.
The Ninth revealed that the Sin in the ceremony was merely a fake. He proclaimed that the real one was in a safe that was impossible to penetrate. Suddenly, the safe was broken open, revealing Large and Enma with rest of the Simon. Enma stated that they came to the ceremony to take back "Sin" for the Simon Famiglia, and get revenge on the Vongola. Tsuna asked Enma why they attacked Yamamoto. Enma responded that he was a Vongola Guardian and it was a "rightful atonement." Enma then went on to explain that the Sin belonged to the Simon Famiglia and that it was the blood of their First Boss. Enma declared that he would take over their Famiglia as the Simon Decimo and take revenge on the Vongola by gathering Mafia from all over the world and standing above them as their leader. The purpose of the war was to gain back the pride of the Simon. Large and the others then released their rings as Enma said that the reason that Vongola Primo got rid of the Simon was because they had a power that rivalled the Dying Will Flames of the Sky, which were the Dying Will Flames Of The Earth. Enma then went on to defeat Tsuna and his Guardians. The Simon Famiglia then took their leave and went back to their home.
He later seen again along with Enma and the others when Tsuna and the others arrived at Simon Island, then at the meeting with remaining guardians of Simon regarding the result of the fight between Ryohei and Kouyou and about the memories of Cozzato and Giotto, and lastly when Lambo fell to the pitfall, he appeared before Lambo, seemingly ready to fight him.
Large tells Tsuna that the dome is held up by the strength of the walls and if Tsuna manages to break out, the dome would fall apart and Lambo would be trapped underneath. He also says that the surrounding rocks are rich with minerals and crystals, an ideal location for his abilities and that fighting there means a simple victory for him.
Lambo ignores Large and tells him that he's his master and Large must obey him. With anger Large says that he's Lambo's slave no longer. Lambo stills thinks it's a joke and laughs. Large, very angered, stomps on the floor without intentions of letting Lambo live. Because of this, Lambo cries and he upgrades his old Vongola Gear and it transforms into the Lighting Helm Version X. Lambo says that the helm is too tight. With this, Large says that they are going to fight like sumo wrestlers and whoever falls from the dome is the loser. Large attacks Lambo and seemingly knocking him out of the dome and says that he's the winner because even if he survived that fall, Lambo is out of the dome. He then laments that if Lambo had not been a Vongola and were a few years older, they could have been good friends. However, the dust settles and 15-year-old Lambo is standing there holding the Helm and claims that from now on they are the same age. The real battle then begins. Large then explains that he is the guardian of the Mountain just as Lambo combines with Gyuudon for his Cambio Forma. Large starts the battle and the two began to strikes each other at the same time. Due to Large's mountain flame that allowed him to synchronized with the earth, Lambo was knocked off by Large but able to kept his balance from falling. Lambo who believes that Large is really bullying him, is now discouraged in fight. But fortunately Tsuna tells tell Lambo that he has to fight, or he will be imprisoned at the Vindice Prison forever if he loses this match. But Lambo becames less willing to fight and starts to cry.
Tsuna and Reborn eventually regret their decision for taking Lambo with them because he is 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. Lambo who is now determined to fight again so he can properly face his younger self. Large says to Lambo that he is only overestimating himself, but Lambo responds that i'll never know if he tries. Lambo now finally remembered how to activate Vongola gear starts charge up his flame. Large comments that his attack for the most part will only injury him, not defeat him. Lambo with his flames, creates iron sand from the battlefield and pulls it towards him and formed his Electrico Ironhorn. Lambo then starts charge at Large with his Ferro Corno Electro Shock. It not only destroys Large's mountain, but also Large's armor and flames, knocking him out of the ring, thus making Lambo the winner of the battle. Large is left in complete shock that he lost, and vows that Enma and the others of the Simon will avenge him. Lambo responds back to Large's claim, and asks if Enma is really that great.
Large tells everyone that when they still growing up in past they were persecuted by the other mafia families under the umbrella Vongola and lost their families. Large states because of that, the bonds of the Simon are strong, since the they share each other's sorrow and hatred. Just then, the Vindice appear behind Large and chain him. But before leaving, the Vindice guards show both Simon and Vongola guardians a flower that was the second key the left by Giotto and Cozzato, which contains another one of their memories. Large is in disbelieve in what he witnessed in the second memory of the Primo and the Simon Primo's past. Gokudera interrupted that only a great person will be chosen as Vongola and pointed out that Large himself was beaten by one of the Vongola guardians. The angered Large asks Lambo if Tsuna is a good boss, which Lambo answered that he never thinks of Tsuna as his boss, much to the shock of Large and Tsuna and Gokudera's anger. However, he stated that Tsuna is a great brother which Large wonders that can be a form of boss. Large is later seen being taken away by the Vindice and shouts that he could never forgive Vongola, but he accepts Lambo, and said that it was fun.
At the end of Demon and Tsuna's battle, he and the guardians of both families are released from the Vindice Prison and he reconciled with Lambo. A week after the battle, he is seen with Lambo at the gate of Namimori-Middle after playing with Lambo since three in the morning (he actually meant three in the afternoon), telling Tsuna that the Disciplinary check was postponed because Hibari left for Kokuyo.
Large is first briefly seen dissuading Adelheid into "taking care" of Skull, stating that they couldn't take care of babies.
Later, when Adelheid stumbles upon Enma and Skull after them nearly getting killed by Team Mammon on the first day of the Representative Battle of the Rainbow, Adelheid thanks Skull for saving Enma and agrees on behalf of the other Simon Guardians to become part of his team in the Representative Battle. Thus, Large joins Team Skull.
On the second day, no one challenges Team Skull until just before the battle ends, whence a group of Vindice that eventually become known as Team Bermuda appear and defeated all of Team Skull in an instant, stealing their Rainbow Wristwatches to enter the battle as well. Team Skull is mortally wounded, but still alive at this point.