Izzy looks up to Tai as a leader and values his opinion very much. The Digimon Adventure novels reveal that Izzy had joined the soccer club at school in order to fulfill a physical education requirement and had been invited to summer camp by Tai; thus, he is indebted to him. Izzy also notes that Tai treats everyone equally, without discrimination.
Izzy and Matt get along fairly well; they at least do not get into as many arguments as Tai and Matt do. When Matt realizes Tai and Agumon weren't back from Pixiemon's training, he and Izzy decide to go off and find Tai themselves while everyone else rested. Usually Matt is impressed with what Izzy has to say and always is willing to listen to any new theories that Izzy has formulated. Izzy also likes to hear feedback; he was interested when Matt responded why he wanted to find a crest to "digivolve" or improve himself as well as his Digimon.
Izzy views Sora as a friend. She is not quick to judge his computer hobbies and standoffish behavior, and even once sticks up for Izzy when Tai yanks his computer away from him.
Izzy often finds it hard to come to terms with Mimi's stubbornness and unwillingness to listen to logical reason (although said lack of logical reason turns out helpful in the Black Gear incident). He eventually, however, comes to terms with her down-to-earthness and comes to care for her deeply.
In the manga of Digimon Adventure Mimi and Izzy are trapped in some ancient ruins and Mimi runs off crying about how Izzy likes his computer more than her. Also in the manga, while asleep, Izzy dreams about Mimi: "Sure Mimi, I'll hold your hand."
The Digimon Adventure novels mention that Mimi was Izzy's classmate prior to the series.
While Izzy has a vast knowledge of technology, he looks to Joe for the life wisdom he has to offer. He also is one of the only people besides Kari, and T.K. who understands Joe's full value from the beginning, something Tai, Matt, Mimi, and Sora figure out later in the series. When the group escaped from Piedmon, Joe sacrificed himself and got caught for letting Izzy the chance to get away. However, Izzy got caught himself, not before he cried out for Joe. In 02, it looks like the two become close friends and seen a lot side by side, and of course are helping Cody Hida to become better digidestined.
Izzy is not the closest person to T.K in the first season, maybe because there were other four (Tai, Joe, Sora and of course Matt) who took care of T.K since they were the older ones who had to be in charge, but the two are good friends, and are often seen staying close to one another in most parts of 01. In 02, the two communicate more (maybe because Izzy helped a lot to the group in this season) and teach the new digidestined about the digital world.
When Kari first stepped foot into the Digital World, Izzy was protective of her like his other fellow DigiDestined. However, he did not obsess over her safety like Tai did, and allowed her to prove that she could fend for herself. At Tai's request, Izzy has taken responsibility for watching Kari on two occasions; first when Tai involved himself in WarGreymon's fight with Piedmon, and next when Izzy partnered with Kari to contact the DigiDestined in Hong Kong.
Yolei looks up to Izzy,as he was president of the old Computer club.
Izzy seems eager to pass on what knowledge of the digital world he has to Cody. The two boys share the same trait of the Crest of Knowledge thus making them rather compatible peers.
|Main characters:||Taichi "Tai" Kamiya | Yamato "Matt" Ishida | Sora Takenouchi | Koushiro "Izzy" Izumi | Mimi Tachikawa | Joe Kido | Takeru "T.K." Takaishi | Kari Kamiya|
|Digimon:||Agumon | Gabumon | Biyomon | Tentomon | Palmon | Gomamon | Patamon | Gatomon|
|Villains:||Devimon | Etemon | Myotismon and DemiDevimon | Dark Masters | Apocalymon | Diaboromon | Millenniummon|
|Other characters:||Gennai | Willis, Gummymon, and Kokomon | Ryo Akiyama | Koromon | Leomon | Ogremon | Wizardmon | Other characters|
|Relationships:||Taichi "Tai" Kamiya | Yamato "Matt" Ishida | Sora Takenouchi | Koushiro "Izzy" Izumi | Mimi Tachikawa | Joe Kido | Takeru "T.K." Takaishi | Kari Kamiya|
|Other media:||Digimon: The Movie | Digimon Adventure | Our War Game! | Digimon Grandprix! | Character Song + Mini Drama 1 (2, 3) | 2½ Year Break | Anode/Cathode Tamer | Novel | Albums | PSP game|
|See also:||Digimon | Digital World | Digivice | Crests | Black Gear | List of episodes|