The day that TK went missing was the day that the change began to start. All of the digidestined got together to help in the search. Plans were dropped, appointments forgotten, and school was put on the sidelines that they all frantically searched for their good friend. They found nothing. There was no trace of where he had gone. No one had even seen him emerge from his room that day. It hit everyone hard, and for months they continued the search, but it was of course Matt the searched with the most frantic fervor.
It was one day while Matt was milling around TK's room, hands lightly grazing his brothers' things just to feel close to him. He opened TK's drawers of his desk in hope of finding some clue as to where the boy had gone, only to find nothing. That's when it hit him - they had been looking for something when they had forgotten to take note in the absence of something.
"Matt, what's up?" Sora looked at him worriedly as the digidestines gathered together.
"His digivice is gone." Matt said, eyes wide, and there was a stunned silence that descended across the group.
"So you think he's…" Tai started, looking off to the side.
"He must be in the digital world!" Davis said enthusiastically and Izzy was already pulling out his laptop.
"I was supposed to get pinged when the portal opened but I guess that…" Izzy frowned at his computer. "...that it's not open after all."
"Then how did TK get in?" Yolei asked, peeking over Izzy's shoulder. That remained the conundrum for the next few years. The group worked together for a while trying to get the gate open, or contact the digital world, but to no avail. Something changed in Matt, during those few years. He became bitter towards the digital world and digimon - he began to think of it as the evil that had spirited away his younger brother, and something in his heart hardened.
He managed to convince everyone that hiding the digital world would be best for everyone, they were all moved out of their homes by now. Most people were convinced shortly after an extremely negative attempt at punching through to the digital world which resulted in destroying most of Odibah, which was then absorbed by Shinjuku causing that city to grow quite large. They all changed their names and identities after that, shock at what they had done creating fear. Many of them stopped working on the project after that.
Matt, in furious rage, split off from them and to start his own company where they could protect the world from Digimon ever appearing again. He insisted that there would never be another incident like what had happened to his brother. The only person to follow him was Yolei, partially because she knew that he truly didn't want to be alone, and partially because Sora had asked her to watch him.
Davis ran a noodle cart in Shinjuku before finding a women and settling down with a family in a bakery. Together they had a son, and named the boy Takato. Cody began teaching martial arts to children. Ken stayed with Jo, Tai, and Izzy for a while and worked on the Digital World project, in the process starting the Digimon card game series to help keep them afloat, but with time both him and Jo broke off to live their own lives. Ken had a complicated marriage that ended with him alone with his one son, Kenta.
Mimi and Jo briefly considered being together, dancing aroung the topic of romance, until eventually Mimi with her free spirit went off to the explore the world, almost never touching back down in Shinjuku until several years later she had a daughter, who she called Rika (she never did find out who the child's father was). Jo worked for some coding companies, partially bemoaning his dreams of being a doctor, and was surprised a number of years later, holding a newborn Henry in his arms, that he was happy.
Izzy and Tai never gave up, no matter how long they had worked. They separated themselves from the other, as per the other's wishes to start new fresh lives, but they never went by nor called each other fake names like disguises. Kari stayed with Tai for sometime, hurt and never getting over the loss of TK, before deciding to live out her dream as a teacher, and try to be busy enough to forget what she was missing.
For a brief period of time Matt came to his senses and got together with Sora again. They were happy in their little bubble of happiness and love, but the pain of losing his brother inevitably came back and the two fought. They fought because Sora would love him but couldn't be with a man with so much anger at the world in his heart. They separated again and a few months later Sora had their child, Kazu.
And then, 15 years later, give or take one or two, an unconscious boy shows up at the Matsuki's household.
