A month before Varia's arrival, Moose, Ken, and Chikusa attempted a jail break. Moose used himself as bait so the others could get away and as a result, was thrown into a lower level jail cell. He later discovered Chrome Dokuro, and became the Vongola Mist Guardian in exchange for his comrades' safety. During the Mist Ring Battle, Chrome was defeated by Mammon. Moose then appeared briefly and defeated Mammon himself. It is revealed by Chrome that Moose knew Xanxus's plans and asked Lancia to help them after the battle. In the future, Glo Xinia claimed to have defeated Moose during a previous battle. However, Moose had in fact possessed Glo's Owl Box Weapon and used this to help Chrome defeat Glo Xinia at Kokuyo Land. He spied on the Moose under the disguise of Leonardo Lippi, sending information of the Millefiore to the Vongola, but ends up being injured in a fight against Byakuran, who claimed to have always known his true identity. Moose planned to leave his body after gathering infomation about Byakuran's power, but was stopped by him as he blocked out Moose's power to transfer his consciousness out of Leonardo's body. After this, Moose's fate is unknown; however, he managed to leave a message about Shoichi Irie's round device to Chrome and Tsuna in their dreams.
Moose left Chrome behind in Kokuyo Land with a letter that telling her to get out and a Namimori-Middle uniform. Shortly after, he convened Reborn to talk about Chrome and explained that he wanted to get ahold of Flan who was living in France and thus, leaving Chrome in Namimori along with her living expenses, but not telling his reason for leaving her.
When they arrived in countryside of France called Jura to recruit Flan to their team, they ended up meeting Varia. When they found Flan, Moose approached him as his master but quickly furious once Flan mistook him as fairy and compared his hair with pineapple. Both he and Squalo said to each other that they could have Flan. Moose refused to take Flan into custody since he's busy and cannot stand his stupidity that needs to be cured first with Varia's facility and then afterwards, he will get him back. After the arguments with Squalo, they decided to conclude with a game of ladder with the loser must take Flan into their custody. However, Flan interrupted and stated that he already decided which group he will go with, later revealed that he has chosen Kokuyo. Afterwards, Moose and his gang went back to Kokuyo Land and he was seen talking with Verde, who asked him to At the park, he encountered Tsuna, Reborn, Yamamoto, and Gokudera. They questioned what he was doing in Namimori, but he didn't feel like answering them and ready to fight. Moose's team arrived just in time as the watch announced that the time limit would be twelve minutes. Ken and Chikusa able to rejoin the battle by using the spare watches that hadn't been used. When they were about to start, however, three Vindices arrived. Verde suggested that they should temporarily team up with team Reborn, but Moose refused, confidently saying that with Ken, Chikusa, Flan, and Verde's invention, they could win against both team Reborn and Vindice. Flan, unfortunately, was asleep. Ken tried to wake him up, but Flan is sleep talking and didn't wake up by Ken's call. The Vendices attacked Moose and Tsuna, but both able to block their attacks. Having no other option, Moose and Tsuna decided for a truce and fight the Vindice together temporarily.
With combined efforts of both teams, they able to rip off Vendice clothes and witness their true forms with stone pacifiers similar to the Arcobaleno's each around their necks. The Vindice, Jack, complimented them as the first people to be able to rip off their clothes and saw their true forms before proceeding to attack them again. They easily overpowered Yamamoto, Gokudera, Ken, and Chikusa, knocking them unconscious and leave only Moose and Tsuna to fight. Moose ordered M.M to wake up Flan as they were at disadvantage, but Flan fainted again once he saw the Vendice. Realizing that he had relying on Flan too much, he decided to take the matters alone, unleashing Genjuu Gagaia. However, unlike the previous attack, the Vendice are able to destroy every single crow.
As he and Tsuna both cornered, Chrome arrived as Reborn's sixth representative, offering to support Moose's illusion. Seeing Chrome's weak condition, Tsuna questioned why Moose didn't help providing her with his illusions. Moose refused to answer, telling him that it was none of his business which angered Tsuna who then asked did he abandoned Chrome, much to Moose's annoyance. Reborn told Tsuna to calm down as it wasn't Moose's fault but Chrome's own problem, revealing that Chrome rejecting Moose's illusions because she wants to be acknowledged by him. At the same time though, some part of her keep wanting to live with Moose's illusionary organs, making Chrome trapped within her own dilemma. This made Reborn understood Moose's decision to leave Chrome in Namimori as he wanted to keep a distance between them since Chrome's heart has been struggling. Moose stated that he wanted Chrome to become an independent soldier who can stand up on her own as he saw great quality of a warrior in her and he would acknowledge her once more if she were to come against him as part of Team Reborn, something which Tsuna disagreed. Once Chrome finally able to found her resolve, she support his illusions, using full power of her flames. This impressed Moose as her flames are even stronger than Flan but then soon turned into shock when he realized that the tranquility of her flames is different from usual, feeling his heart was being healed. With their flames at the fullest power, he and Chrome unleashed a much powerful version of Genjuu Gagaia, Genjuu Mugaia, defeating two of three Vendice.
After Tsuna defeated Jaque and being sucked into Bermuda's warp hole in attempt to prevent Reborn being taken away and the third day battle ended, he and his team except M.M and Flan returned to Kokuyo Land to treat their injuries. Shortly after, Tsuna visited Mooseto discuss something with him. The next day, he and Kokuyo Gang members, along with other people who Tsuna had contacted yesterday night gathered at Tsuna's house. There, Tsuna requested for all of them to fight together.
When Bermuda and Jager received report that Team Verde members they defeated were decoy puppets like other two teams, Jager suggested that they should go to where Big Pino and Small Gia are to prevent them being defeated one by one. However, Moose, Dino, Squalo, Xanxus, and Byakuran revealed themselves from their cover, preparing to fight them to prevent them from assisting their teammates. After Jager defeated Squalo, Byakuran, and Xanxus, Jager begins to attack Moose, but Moose able to defend himself, avoiding grave injuries. After Dino was defeated, he and Hibari fight together against Jager until Tsuna arrives. Finally realizing that Jager only able to short warped his full body twice, Moose and Hibari protected Tsuna and Moose stopped Jager's movements by freezing his arms while the latter stabbed through their shoulders, giving Tsuna a chance to defeat Jager with converted X-Burner. Heavily injured, Mukuro and Hibari collapsed, unable to fight any longer. Before Tsuna could finish Jager, Bermuda interferes and released his curse and destroys the battler watches of the collapsed team members, disqualifying them and only leaving Tsuna and Reborn to fight Bermuda.
After Bermuda was defeated and Arcobaleno's curse are removed, Moose, Chrome, and Flan are submitted into Namimori Hospital along with the Varia, Hibari, Byakuran, Dino, and Basil, much to Tsuna's surprise. When Hibari was angered by the interruption caused by Xanxus and Byakuran, he destroyed the wall that led to Mukuro's room, making Moose and other Kokuyo Gang members who are visiting them startled and he accidentally crushed his chocolate ice, which angered Moose and they started to fight, destroying some parts of the hospital. In the final chapter, Moose is last seen along with his gang when Tsuna narrates his thought of how now he has friends that he could rely on when it's necessary.