Let me explain the Oikawa thing.
After Tai and the other 7 chosens defeated VenomMyotismon in 01, Oikawa from afar saw the column of light who took the digidestined back again to the digiworld, he shouted at them to take him with them (not like they heard him since he was far away from them anyways XD), then Myotismon's soul, data or whatever to call that mist that was what remained of him offered Oikawa to help him to reach the digiworld if he helped him, of course ommiting any details like who he is, etc. that could make Oikawa refuse.
Of course Oikawa accepted the offer and that myst entered in his body. Myotismon used Oikawa's body as host during more than 3 years, maybe 4 since it was from the remaining of the first adventure and the whole 02 except for the last two chapters. This also explains the changes Oikawa suffered like growing his hair long, the gray skin, etc. Myotismon not only used him as host but also sucked off Oikawa's life force.
Oikawa saw Ken during Sam's funeral. It was there when he knew Ken could be useful for him, so he sent Ken that misterious e-mail he got which ultimately lead him to the dark ocean and to awake the Digimon Emperor thanks to the dark spore he already had on him from a past trip he did to the Digiworld along with believe it or not Ryo Akiyama. You even can see Ryo with Ken during one of Ken's flashbacks in the series.
Oikawa also created Arukenimon and Mummymon combining his dna with data, hence that Arukenimon and Mummymon can change between their digimon forms and human forms so they could wander in the real world without anyone suspecting.
All of this was part of Myotismon's plan. When Ken stopped being the emperor and the digidestined foiled the destruction of the last destiny stone, Myotismon settled for another plan. He made Arukenimon plant the control spears in the real world and somehow released digimon in 7 places in the world: Japan, Mexico, USA, France, Russia, Australia and China, thus the world tour started.
This also was a distraction since while the digidestined were taking care of that problem (World Tour), Oikawa along with Arukenimon and Mummymon convinced several kids who were having problems and were depressed to follow them. They had planned to get Ken and clonate the spore on his neck to implant it on those kids.
When the digidestined return and take a little break, and before Oikawa could do a thing, Daemon and his corps attacked. Apparently Daemon also wanted that spore Ken had on his neck. His reasons are unknown though, actually Daemon wasn't even connected to Myotismon/Oikawa hence Daemon interecepting the truck Mummymon was driving and in which he and Arukenimon along with Oikawa were transporting the kids, but by the time Daemon managed to intercept the truck, Oikawa already had cloned and implanted the spore on the other kids.
After sealing Daemon in the dark ocean and Ken explained the others what Oikawa did to those kids, the digidestined started to watch them. Also they got help from Mrs. Takaishi, Mr. Ichijouji, and if my memory serves right even from Mr. and Mrs. Izumi. Also Cody's Grandpa got some impact on this part of the series since he was a key character on this since he knew Oikawa due to that Cody's father and Oikawa were childhood friends.
What Myotismon planned with those kids was let the spores grow on them to then take them to the digiworld and there he would take the blossomed spores from them and absorb them and in that way get his real body back and dispose of Oikawa but when BlackWarGreymon sealed the gate in Highton View Terrace (Hikarigaoka in Japan) they ended on that strange dimension where what you wish it would come true, which actually is part of the reason on how the digiworld got formed. The digiworld got created from data and human thoughts, the dark ocean got created in that way too but all the human thoughts were the negative ones.
In short what Myotismon planned was his return but each time he plotted anything the digidestined stopped it without knowing he was behind it. The Control Spears and Kimeramon were the first attempt, with that heavy unbalance he could gather enough darkness to return but the digidestined foiled The Digimon Emperor's plans. Then it came BlackWarGreymon and the destiny stones. By managing to save the last stone and Azulongmon planting the seeds of hope on the places the other stones once occupied, Myotismon second attempt failed. It was only on his third attempt, the dark spore kids that he managed to return but still you know how it ended.
So there you have the story about Oikawa ^^
yay another plothole.... uh... when all the forms of the Digimon appear how come Veemon is missing Paildramon, I-dramon, and I-dramon FM and also me
Err... you really need glasses man, Paildramon, Imperialdramon and Imperialdramon Fighter mode were there with all of the other digimon when they released all the digivolutions in the dream world.
Only Magnamon was missing but that is because Davis doesn't has that digiegg on his D-Terminal plus it would have been too much having Magnamon there too Davis got enough already with what he got out of Veemon's forms to battle MaloMyotismon o.o
