Yu Nogi/Partners

SkullSatamon
SkullSatamon is one of Yu's Partners. It destroys parts of various cities alongside K, leading Keisuke Amasawa to challenge him to a fight to stop him. Keisuke is easily defeated, though before anything happens to Keisuke, Ryuji Mishima and his Arcadiamon (Rookie) appear, easily defeats SkullSatamon and then is absorbed by the powerful rookie level Digimon. With nothing to protect him, K flees.

Gazimon
Gazimon is one of Yu's Partners. It appears as part of Yu's team in Domination Battles. After Digimon arrive in the real world, Yu's Gazimon has digivolved into Garurumon (Black) when helping Keisuke in Domination Battles. By the time of the Master Cup, it has Digivolved into a Pandamon.

Wizardmon
Wizardmon is one of Yu's Partners. It appears as part of Yu's team in Domination Battles. By the time of the Master Cup, it has digivolvled into a Phantomon.

Gekomon
Gekomon is one of Yu's Partners. It appears as part of Yu's team in Domination Battles When Yu takes part in a territory battle alongside Keisuke Amasawa, it has digivolved into a Whamon. By the time of the Master Cup, it has digivolvled into a MarineAngemon

Other Digimon
Zaxon contacts Hudie and tells that that they're attacking the Demons and not to get involved. Keisuke Amasawa however, had already agreed to a meeting with K at the Demon's Den. K had told Keisuke to go alone, which he planned to do. Wormmon however was sent by Erika Mishima to spy on Keisuke to make sure he was okay. Wormmon winds up revealing himself to Keisuke and states that since he's a Digimon, he doesn't count as a "someone", so it clearly means Keisuke would still be "going alone". Ryuji Mishima however, after finding it suspicious that Keisuke hadn't turned up for work that day, pressures Erika and causes her to reveal Keisuke's plan to meet up with K. This pisses off Ryuji, who then tracks Keisuke down and demands him to cancel the meeting with K. After Keisuke refuses, Ryuji forces Keisuke to take him with him as well. Ryuji and Wormmon plan to hide during their meeting, just to make sure nothing happens to his employee.

Whilst Jimmy KEN hosts a rally for the members of Demons, Keisuke Amasawa eavesdrops in the distance, hidden from Jimmy KEN, awaiting K. K was also eavesdropping however and spots Keisuke, which leads to their first ever face to face meeting, though rather than discuss anything hacker related, K instead begins talking in riddles and begins claiming that Keisuke isn't real and a host of other confusing things. Ryuji Mishima and intervene as he was pissed off with what K had been saying to Keisuke, whilst K becomes pissed off due to Keisuke not coming alone. In retaliation, he summons four Digimon, Airdramon, Dorugamon, Raremon and Kurisarimon. K flees the Demon's Den and controls the four Digimon remotely, which Wormmon comments makes him an extremely talented hacker. The three of them team up to kill the four Digimon, though have to accept that K had gotten away. Ryuji tells Keisuke not to contact K ever again, though Keisuke does so multiple times anyway. Also happening during the fight against the four Digimon, Nokia Shiramine, Fei Wong Tomoe Ignacio and Kamashiro arrive and defeat Jimmy KEN, deleting his account - which causes Jimmy KEN to go into hiding, allowing K to take over control of Demons.