Taichi and Agumon land back in the other world, where Taichi's Digivice leads him to a lake. There, they find a collapsed Tokomon along with Takeru's Digivice and Crest. Tokomon is surprised to see Taichi and Agumon, and tells them that Takeru is with a Digimon named PicoDevimonnote .
Tokomon explains that in the terms of this world, Taichi and Agumon have been gone for no less than a month and a half, and that the others started leaving one by one to look for Taichi and Agumon by themselves, until only Takeru, Yamato, Tokomon, and Gabumon remained together. A frustrated Yamato had given up on the search, but Takeru was still insistent that Taichi must be alive somewhere, and together they wandered around until they reached a mysterious amusement park. Entrusting Takeru to Tokomon, Yamato and Gabumon went off in a swan boat to check the area out, but didn't return.
Takeru became increasingly depressed and panicky until they were approached by PicoDevimon, who offered to find Yamato but returned with a message that Yamato "doesn't want to see your face anymore", "doesn't want to be your brother anymore", and "really hates you for being a crybaby". Tokomon didn't buy it, but Takeru lapped it up and broke down, and when Tokomon attacked PicoDevimon for lying to Takeru, Takeru took PicoDevimon's side and PicoDevimon claimed that Tokomon was jealous of him and Takeru getting along. Takeru tried to get Tokomon to apologize, but Tokomon proclaimed that he'd rather leave and did so. Knowing that they need to take care of Takeru, Taichi and Agumon ask Tokomon to lead them to where Takeru is.
A pair of Gazimon contemplate taking revenge on the Chosen for Etemon, but quickly decide to wind down and eat some nearby mushrooms instead.
PicoDevimon tries to entertain Takeru with the amusement park attractions, but Takeru is still worried about Tokomon, which bothers PicoDevimon. Takeru is soon found by Taichi, Agumon, and Tokomon, and is overjoyed to see them but wants Tokomon to apologize. Taichi wants to get Takeru to help him find the others, but Takeru, frustrated at having been left alone by everyone and attributing it to himself being a crybaby, wants no part in it. Telling Taichi that he believes Yamato dislikes Taichi, since he had an angry look on his face every time Takeru brought him up, and that Yamato was probably driven away by Takeru talking about him, Takeru wants to be Taichi's younger brother instead.
PicoDevimon finds the Gazimon pair and realize that they've forgotten everything right down to their identities; realizing that the mushrooms they've eaten cause the victim to forget everything, he decides to use them on Takeru. He returns to see Takeru joined by Taichi and the others; Agumon questions him on what Yamato really told him, but PicoDevimon claims that Yamato really did say he hated Takeru and that PicoDevimon couldn't get him to change his mind.
Trying to defuse the situation, PicoDevimon offers them the mushrooms, and Taichi decides to cook them so they'll taste better. Agumon goes off to the bathroom, and on his way finds more of the mushrooms, but upon inspecting them, hears a voice telling him that the mushrooms will take away all their memories. Alarmed, Agumon goes to inform Taichi and Takeru, while from behind a bush Sora and Piyomon look on them...
Agumon returns just in time to stop Takeru from eating one and reveals the mushrooms' properties by attempting to make PicoDevimon eat, and he refuses to do so for obvious reasons. With PicoDevimon's nature exposed, Takeru apologizes to Tokomon, and Taichi gives him back his Digivice and Crest, the latter of which begins to glow. PicoDevimon demands the Digivice and Crest, but Takeru's Digivice lights up and Tokomon evolves to Patamon.
Patamon drives PicoDevimon away, and rekindles his friendship with Takeru, who's now eager to find his brother again. Taichi praises Agumon for figuring out the mushrooms, and Agumon tells him that he found out because of a voice — but doesn't know whose.
PicoDevimon reports to a mysterious cloaked figure and tells him that "the Crest of Hope has regained its light"...
Taichi tells Takeru that the distortions of the Digital World are affecting the Real World, and that they need to set things straight before they go home. With that in mind, they go off to find the others.
- Festering Fungus: The Mushrooms of Forgetfulness apparently take root into the people who eat them — the two Gazimon who ate their way through a patch of them had toadstools growing all over their bodies by the time DemiDevimon finds them.
- Identity Amnesia: After eating the Mushrooms of Forgetfulness, the two Gazimon forget their old job as Etemon's minions, their location and even their names.
- Let's Split Up, Gang: The main characters quickly split apart once Taichi and Agumon vanished — Sora and Biyomon left to search from them on their own, then when the rest went to search for them they decided they'd cover more ground if they split up, so Izzy and Tentomon went off one way, Joe and Gomamon went another and Mimi and Palmon went yet another, leaving Matt, Gabumon, T.K. and Tokomon by themselves. Then Matt and Gabumon left T.K. and Tokomon at an amusement park they found and never came back, and T.K. left Tokomon after they fought over T.K. spending time with DemiDevimon.
- Magic Mushroom: The Mushrooms of Forgetfulness, which if eaten cause one to lose their memories.
- Mysterious Protector: Sora, who secretly whispers a warning to Gomamon about the Mushrooms of Forgetfulness, foiling DemiDevimon's plot without the other characters realizing her role.
- What Happened to the Mouse?: The two Gazimon that lost their memories are never brought up again.