Creating Guilmon and learning about Digimon
Takato and his parents live in a house with a bakery. Takato would often play the Digimon card game with Kazu. On one fateful day, he found a Blue Card and slid it through his card reader, transforming it into a Digivice. He was late for school that day, and while in detention he designed a Digimon called Guilmon, drawing a picture and writing information on him. That night, the picture and papers on Guilmon slid through his digivice, creating a Digiegg from which Guilmon later hatched. That night, Takato witnessed in his dream a battle between Renamon and Lynxmon.
Upon discovering that the Digiegg hatched, Takato tracked down Guilmon, whom he tried to hide from his parents, as his mother forbad him from having pets in his house. When Guilmon followed Takato to school, Takato searched for him and met Henry Wong and his partner Terriermon. Shortly after finding Guilmon, Takato found a place in the park for him, but Rika told Renamon to destroy Guilmon, until the fight was broken up by Henry and Terriermon.
Takato and Henry eventually found Calumon and tried to find a tamer for him, until they decided maybe he didn't need one. They also got angry that Rika had Renamon kill Digimon only so she could absorb their data.
When Guilmon was captured by a digital zone, Takato was able to rescue him, with Henry and Rika (whom Takato former a slightly better relationship with) helping him out.
Takato lost trust for Guilmon when he thought Guilmon terrorized couples in the park with fireballs. During Guilmon's fight with Devidramon, Takato heard that the culprit was really Impmon, getting over any trust issues with Guilmon and enabling him to digivolve into Growlmon. After the battle, Takato spent a great deal of time trying to dedigivolve Growlmon, and later hide him, until he finally dedigivolved at a rainbow.
After using a Digi Modify combo on Guilmon to destroy IceDevimon, Takato used the same combo to beat Kazu in a card game. When Kazu beat him in a revenge rematch, the resulting argument caused Takato to show Guilmon to Kazu and Kenta. After he did, they thought he was using a cheap trick and lost all interest in Digimon, refusing to talk to him. However, when Takato showed Guilmon to Jeri, she found him to be cute (to which Takato preferred "cool").
Enter the Devas
When Mihiramon arrived, and Growlmon fought him, Takato felt every bit of damage Mihiramon inflicted on him. Takato thought he wasn't a worthy tamer, but after a vision, he enabled Growlmon to Matrix Digivolve into WarGrowlmon, who destroyed Mihiramon, ending any negative feelings Kazu and Kenta had toward Takato and Digimon.
While Takato was on Digimon Patrol while Henry and Rika couldn't, he ironically was playing with Guilmon, Kazu, Kenta, and other students from school while Henry and Rika became caught in the battle with Sandiramon. After Impmon informed them of this, Takato and Guilmon entered the subway and destroyed Sandiramon.
Takato and Henry took Guilmon and Terriermon with them on a field trip, fighting and destroying Sinduramon. Although Takato witnessed the fight with Pajiramon, Guilmon was not present as they could not find a way to bring him along on their trip. Growlmon did fight Vajramon when he returned, but in the end it was Renamon in her ultimate form of Taomon who destroyed him.
Battle of Adventurers
Takato went on a vacation to an island with his cousin Kai, who became friends with Guilmon. They got caught up in a battle with Mephistomon's henchmen, Takato traveling with Guilmon, Seasarmon, and Kai to rescue Minami from them. In the end they battled in Mephistomon's digital world and Guilmon, Terriermon, and Renamon digivolved to their ultimate forms and destroyed Mephistomon in his Mega form of Gulfmon.
The Devas - continued
Using a blue card that Kazu drew for him, Takato was able to Matrix Digivolve Guilmon again enabling him to destroy Indramon. When Vikaralamon attacked, he nearly killed WarGrowlmon with his Fusion Ball, but Takato and WarGrowlmon used their energy together so WarGrowlmon could break free, throw the giant pig to the ground, and destroy him.
Shortly after, Calumon was kidnapped by Makuramon, and after he and Guilmon discovered a portal to the digital world in Guilmon's cave, Takato told his parents about Guilmon. His mother opposed the idea of him going to the digital world or traveling with Guilmon, but his father felt differently, saying Takato has been able to take care of himself and promising bread shaped like Guilmon when he returned.
With a com device given to them by former enemy Yamaki, Takato traveled to the digital world with Guilmon, Henry, Terriermon, Rika, Renamon, Jeri, Leomon, Kazu, and Kenta to rescue Calumon. When Rika, Renamon, Kazu, and Kenta were separated from the group by a data stream, Takato and the others searched for them and saved the Forgotten Village of Chuchidarumon from the motorcycle, Behemoth.
Afterward they tracked down the flag they used to mark the spot where they arrived in the digital world, and followed Renamon's scent to find the four, but lost them due to another data stream, and took an elevator to a warped area where Ryo and Cyberdramon reunited them with Kazu and Kenta. Ryo and Cyberdramon left the group after destroying Majiramon. Eventually Rika, Renamon, and Calumon reunited with them, but this was short-lived. After a battle with Impmon in his Mega form Beelzemon was averted, Caturamon captured Calumon and sent Takato, Henry, and Terriermon flying into a data stream.
After reaching a cave in an underwater area, Takato, Henry, and Terriermon discovered that you can breathe underwater in the digital world, and found Shibumi, who explained the digital world for them and gave them an ark so they could find the others. However, they turned aside when Henry's sister Suzie was transported to the Land of the Sovereign in the digital world.
When Beelzemon attacked, Takato initially tried to reason with him, but eventually resolved to destroy him. When Beelzemon destroyed Leomon, Takato was sent into a rage, causing Guilmon to digivolve into an evil form, Megidramon and destroying his digivice. After Beelzemon knocked Megidramon to the ground, Takato was able to restore him to his senses, and biomerged with him into Gallantmon, who destroyed Behemoth and Caturamon and defeated Beelzemon, but spared him at Jeri's request.
Afterward they confronted Zhuqiaomon, but this time it was Henry and Terriermon who biomerged. Zhuqiaomon survived the battle, and later Takato and Guilmon became Gallantmon again and fought Zhuqiaomon before Azulongmon broke up the fight in favor of fighting the true enemy, the D-Reaper.
After rescuing Calumon, Takato and the others returned to Earth. Takato was nearly left behind along with Rika, Renamon, and Impmon, but when Guilmon told the ark (created by Janyu and Dolphin to return the tamers home) to stop, it listened to him, so no one was left behind. Takato took Jeri (who by now had been replaced by a D-Reaper agent in disguise) home, and discovered that the D-Reaper returned to Earth.
After Beelzemon helped them destroy a powerful D-Reaper agent, Takato saw "Jeri" behind a tree and thought her to be a ghost since she couldn't have gotten to this point in such a short amount of time. During the battle with D-Reaper agent Creep Hands, Alice and Dobermon gave the tamers and their Digimon the ability to biomerge on Earth. Gallantmon destroyed Creep Hands but was pulled into the D-Reaper's mass of chaos where he separated. Takato and Guilmon were then chased by Evil Jeri as she revealed her true identity, but were saved by Kenta and his partner MarineAngemon.
Eventually Gallantmon gained a steed in the form of the transformed ark, now going by the name Grani, enabling him to destroy the giant D-Reaper agent Optimizer. He also helped Beelzemon try to rescue Jeri, but this failed, and when the D-Reaper continued to evolve, the tamers were forced to retreat for a week. Eventually they returned for a final battle with the D-Reaper, and Gallantmon went to rescue Jeri, with Grani merging with them to turn him into Crimson Mode. Gallantmon destroyed Evil Jeri before the D-Reaper was sucked into the void of Juggernaut. However, due to a miscalculation by Shibumi, he and the others separated. Takato and Guilmon got to Jeri but were nearly sucked into the void until they were saved by Kazu, Kenta, and MarineAngemon.
Guilmon and the others were forced to return to the digital world due to the effects of Juggernaut, but Takato found the portal inside Guilmon's cave reactivated and was able to return the Digimon to Earth.
While setting up Rika's birthday party, Takato and Guilmon became caught up in a battle with Locomon, who turned out to be possessed by Parasimon. In the end it was Gallantmon who destroyed Parasimon and his gang by destroying their digital zone with Crimson Light. Takato is last seen at Rika's birthday party walking down the hall with Renamon.
- Takato is hinted at a romantic relationship with Jeri. It is also hinted that he might be in love with Rika upon their reaction to Terriermon saying "Renamon and Guilmon sitting in a tree".
- Takato designed Guilmon to be very similar to Agumon, due to being a fan of the Digimon Adventure/02.