Koushiro "Izzy" Izumi (泉 光子郎, Izumi Kōshirō?) is a character in the anime and manga series Digimon Adventure and Digimon Adventure 02.
He is partnered with Tentomon. Izzy is a computer expert and spends a large fraction of his time trying to figure stuff out on his "PiBook" laptop. Izzy lives with his adopted parents. When he initially found out that he was adopted, he began to subconsciously distant himself from his parents and focusing on his computer. The issue is resolved when his parents come forward with the truth and he accepts them as his true parents.
He is the bearer of the Crest of Knowledge. He is one of the core members of the DigiDestined in both seasons.
He saw the battle between Parrotmon/Greymon, resulting in him becoming a DigiDestined. Izzy's real parents died in a car crash, and Izzy's adoptive parents were asked to take care of him. He heard he was adopted on a night when he couldn't sleep.
Izzy is the computer whiz of the group, and the most curious of the Digital World. He often prefers to be alone. Once in the Digital World, Izzy develops an "alien theory" and has a low opinion of the Digimon. For instance, when his partner, Tentomon, hears about Izzy’s alien theory, he asks, "What mystery is there to me? I am who I am." When the DigiDestined enter a factory, Izzy finds a large battery and enters. He wipes away a part of the hieroglyphics on the inner wall, causing the factory to stop production. Izzy becomes the first to realize that everything, even the program, is living in the Digital World.
Izzy’s skills with the computer, however, soon prove to be extraordinarily useful for the group. During the battle against Andromon, Tentomon suggests that Izzy reenter the program that activated his Digivice. When Izzy retypes it in, Tentomon digivolves into Kabuterimon and defeats the black gear in Andromon. When Mimi and Tentomon run into a maze, Izzy pulls out the map and locates Mimi’s location. He then directs her out of the maze.
After the defeat of Devimon, the DigiDestined are sent to the continent of Server to defeat Etemon. While they are in the capacity of Piximon, Matt and Izzy see that their tags are glowing. They sneak out and find their crests; Matt receives the Crest of Friendship, while Izzy receives the Crest of Knowledge. Izzy’s curiosity and deductive reasoning comes in handy once again; when Datamon captures Sora, he is the first to theorize that Datamon is still inside the pyramid. Tai and Izzy rescue Sora. Etemon learns of their presence and goes down there to destroy those kids. In the final ensuring battle, Greymon successfully digivolves into MetalGreymon and defeats Etemon. Tai and his Digimon are sucked into the Real World; during their short stay there, Izzy sends a frantic transmission, warning Tai not to go back to the Digital World.
However, Tai reenters the Digital World anyway, because he knows that he must restore the balance between the two worlds. Izzy runs into Vademon, who tricks him into giving up his curiosity and regresses him to an accepting mind that does not question anything. Tentomon frantically tries to get him back to no avail; he slowly reverse digivolves back into Motimon and Pabumon before Izzy snaps out of it. Izzy gets his tag and crest and his curiosity back. In the ensuring battle, Kabuterimon digivolves into MegaKabuterimon and defeats Vademon.
During the search for the Eighth Child, the DigiDestined pursue Myotismon into the Real World. Gennai loads a couple of programs into Izzy’s laptops that gives him much information. The first program tracks the movement of Digimon; Izzy sees Raremon attacking Tokyo Bay and rushes out there with Tentomon to stop him. The second program puts up a digital barrier, which stops the Bakemon from taking Izzy and his parents away. Gennai also tells Izzy that the source of Myotismon’s power is in the Fuji TV station and describes the prophecy to him. The prophecy aids them in defeating VenomMyotismon; when Izzy reads the prophecy out loud (it took the Digidestined some time to figure it out), the group follows its lines. Angemon and Angewomon hit Matt and Tai with arrows of hope and light, which leads to Agumon and Gabumon warp digivolving into their Mega forms, which is of tremendous aid in the battle.
During this saga, Izzy’s parents reveal to him that he was adopted. Izzy’s real parents were killed in a car accident, and his father’s distant cousin adopted Izzy. Izzy also reveals that he found out when he overheard a late-night conversation, and says that he retreated into computers to try to forget about what he had overheard.
Izzy’s computer becomes a more valued asset as the DigiDestined battle the Dark Masters. Before, their Digimon partners used to describe the information about the various Digimon that they encountered; now, Izzy has loaded a database of Digimon profiles. When a new Digimon shows up, Izzy names and describes the characteristics to the rest of the DigiDestined.
In the last battle against Piedmon, Izzy was turned into a key chain. After Apocalymon was defeated, Izzy calculated that, because one day in the Digital World equaled just one minute in the Real World, the DigiDestined could stay in the Digital World for 118 years. However, Gennai tells them that the time distortion was fixed with the defeat of Apocalymon, and that the solar eclipse would seal the barrier for an indefinite amount of time. Izzy says goodbye to Tentomon, thanking him for being a good friend.
the digidestind and their digimon now are worshiped by jungle people in an uncharted of the digital realm, at some point, they encountered Sam, Max, and a few others and ever since, then lead to a new found partnership to the shell louge squad.