Willis has two Digimon partners, Terriermon and Kokomon. After the original battle against Diaboromon on the internet, Kokomon vanished while the three of them were playing in a flower field. When Kokomon returned, searching for Willis, he has become infected with the virus that caused all the trouble with Diaboromon. This leads to him stalking and attacking the boy and Terriermon for years.
While the egg that hatched into Botamon appeared before Tai and Kari in Japan, in America, a single Digi-egg hatched into Terriermon and Kokomon for Willis. He bonded with his new friends, who helped him do his chores.
The events of "Our War Game"Edit
Willis, unknown to anyone, thought it would be great to have more Digimon friends and tried to create another DigiEgg on his computer but in the process it is attacked by a virus. Izzy discovers the virus on the internet infecting Willis's DigiEgg. At the same time, Tai is trying to apologize to Sora for getting her a hairclip for her birthday in an e-mail. Izzy arrives at Tai's house out of breath, telling Tai about the newly-hatched Digimon. Tai and Izzy use Tai's dad's computer and monitor the Digimon until Gennai appears in a transmission from the Digital World. He sends Agumon and Tentomon to help stop the corrupted Digimon. Izzy mentions briefly an online friend, Willis, who takes college courses despite being in elementary school helping him with aspects of the situation. The partnered digimon put up a good fight until Keramon Digivolves to Infermon and defeats them. Tai tries furiously to contact and alert the rest of the Digidestined and ends up getting only Matt and his brother T.K.. They find a computer in a barber shop and upload Gabumon and Patamon onto the net. Infermon Digivolves to Diaboromon after Agumon and Gabumon Warp Digivolve to WarGreymon and MetalGarurumon but then they slow down because of the massive amount of e-mails being sent to Tai and Izzy. Tai slaps the computer and freezes it leaving WarGreymon frozen and defeated. Diaboromon then starts multiplying and sets up a timer for 10 minutes as he forces the Pentagon to launch two nuclear missiles: one headed for Colorado (where Willis lives), the other for Tai's neighborhood. WarGreymon and MetalGarurumon wake up and race to defeat Diaboromon, only to find over a million copies of him. Every single copy fires and blast them until they lie defeated. Tai and Matt mysteriously enter their computers and talk to their Digimon. WarGreymon and MetalGarurumon DNA Digivolve to Omnimon who easily defeats all but one Diaboromon. At one minute to go, Diaboromon is still too fast for them to hit, but then Izzy forwards him the e-mails, slowing him like it did to the other Digimon. At the very last second, Diaboromon is destroyed, disabling the missiles. But the virus tracks down Willis and infects Kokomon.
The events of "Hurricane Touchdown"Edit
T.K. and Kari are in New York City taking a picture but are having trouble then Kari senses something. The attention turns to Willis and Terriermon, who engages in a battle with Wendigomon, who keeps telling Willis to "Go back," and loses. Willis and Terriermon journey to Colorado while Kari e-mails Davis to inform him of Willis. After taking planes and taxis, they end up meeting Willis in a truck while Kari and T.K. literally get derailed by Wendigomon (who says "don't interfere," just like Diaboromon). Willis tries to get Davis, Yolei and Cody a lift to his house (in the form of a pizza truck). The ride leaves without Willis and Davis, who encounter Wendigomon which leads to a battle between him, Flamedramon and Gargomon, Terriermon's Champion form. Before anyone is defeated, Wendigomon disappears, repeating his cryptic message, "go back."
Davis and Willis meet up with Yolei and Cody who told Davis that Kari And T.K. aren't here (to Davis's disappointment). Willis doubts that they'll come at all if Wendigomon interfered. After the kids question his knowledge about Wendigomon, Willis reveals he created him but regrets saying so and storms off, while being followed by Davis. Willis reveals the story about Wendigomon, how he became infected and reveals that he was the one who created Diaboromon. Davis offers to help with the rest of the kids and their Digimon. Terriermon overhears the conversation (blaming it on his "really big ears") and offers to help. Willis refuses his help out of concern for his safety but Terriermon talks him into letting him. At Willis's lake, Wendigomon reappears, as expected, but digivolves to Antylamon. He swiftly evades the attacks of Gargomon, Flamedramon, Halsemon and Digmon and throws all the Digimon around like rag dolls. Antylamon sinks into the lake (and changes the scenery), and rises again, but as Kerpymon. He then de-digivolves all the Digimon. However, they still try to fight, but to no avail, as Kerpymon grabs them and is about to eat them when Angemon and Angewomon cut off his arms and T.K. and Kari show up.
Kerpymon changes the scenery again and de-ages the Digidstined, revealing that he wanted Willis to "Go back" in time to when the virus attacked him. Angewomon and Angemon digivolve to their Mega forms, Magnadramon and Seraphimon, to release two Golden Digi-Eggs (the Digi-Eggs of Miracles and Destiny for Willis and Davis). Veemon and Terriermon Golden Armor Digivolve to Magnamon and Rapidmon (Armor), who get sucked into Kerpymon. Inside they see Wendigomon who tells them to destroy the virus. Doing so purifies Kerpymon, transforming him into his vaccine form, who soon dies. After saying goodbye to his new friends, Willis and Terriermon walk back home, and notice the Digi-Egg that will hatch into Conomon, Kokomon's Fresh form. In the movie's final scene, it shows him with Lopmon.
Willis was able to communicate with the DigiDestined because a Japanese girlfriend taught him Japanese. He is especially friendly to girls and flirts with them (preferably Yolei); on the other hand, he is the exact opposite towards Davis Motomiya. While Willis considered Davis strange and rude, Davis found Willis arrogant, which struck a friction between the boys. When Willis revealed how he did not have the heart to fight Kokomon, Davis sympathized with him and promised to fight for him. Although Willis and Davis become friends, there are still points at time where Willis would mock him.
In the end right before Willis leaves, he kisses Kari and Yolei on the cheek before running away. Davis gets mad and Kari says Davis is jealous. Davis claims that if he comes to Japan he won't let him near Kari.
In the end of Book Three, the Digidestined universe and the tamer universe collapsed together to form a single universe. This "new" Willis has never met the Digidestined and has no memory of these events. He also has never gained a partner, let alone the twins from before. He has joined the SDCO group's Project Replica and they were supposed to pair him with a partner, along with Michael Washington (another American Digidestined who lost his partner and memories due to the universes' combining). Due to the chaotic events surrounding the Japanese Prime Minister's murder in Book Seven, the boys learn that the digimon who would have become their partners are likely to be killed. They have taken it upon themselves to rescue these digimon and risk the consequences rather than lose their partners before they have the opportunity to meet them.