Koushiro "Izzy" Izumi

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 nerd and spends all his time trying to figure stuff out on his "PiBook" laptop. He played on the soccer team with Sora Takenouchi and Taichi "Tai" Kamiya (Taichi Yagami in Japan). Izzy lives with his adopted parents. When he initially found out, 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. His color is purple and element is electricity. He is voiced by Mona Marshall in the English version and Umi Tenjin in the Japanese version.

Prelude to Digimon Adventure
He saw the battle between Parrotmon/Greymon, resulting in him becoming a DigiDestined.

Digimon Adventure
Izzy was the brains of the group many times he helped the group out of difficult situations. He is the owner of the Crest of Knowledge, mostly because the fact he is not only extremely smart but also has a hunger for the truth. Izzy discovered at a young age that he was an adopted child when he overheard a conversation one night between his foster parents. It was discovered that Izzy's biological parents had died in a car crash.

Digimon Adventure: Our War Game
In Our War Game, Izzy is the one who first discovers a digi-egg infected with a computer virus on the internet, and then rushes off to alert the others. At first only successful in finding Tai, he plays a key role as the brains behind the attacks that were implemented by Tai and Matt.

Between Digimon Adventure and Digimon 02
In May 2000, Izzy arrived at the Digital World and gave up his Crest power to free the Sovereigns. As a result, Tentomon lost the power to become MegaKabuterimon.

Digimon 02
Although he grew, he is still short compared to the other DigiDestined - he is only as tall as the new soccer team. Izzy seems to have a lot of free time and often stops by the computer club at the elementary school to help the new DigiDestined in almost every episode. He is still into computers and is curious about the D-3s and other items the new DigiDestined have access to.

According to Yolei, he is somewhat revered as the former president of the school's computer club.

Digimon 02: Diaboromon Strikes Back
Like in 'Bokura no Wargame!' Koushiro still was responsible for the planning and execution of the attacks on Diaboromon. He was the one who gathered all the Chosen Children (including Tachikawa Mimi flew in from America) to help defeat Diaboromon and stop the havoc it wreaked on the net and the real world.

Digimon 02: Series Finale Epilogue
By the year 2027, Izzy sets up a research team to study more of the Digital World than what the human population already knows. He has a daughter, with a Motimon, but her mother was not revealed.

Trivia

 * Izzy carries with him a yellow laptop that has a pineapple on it, a likely reference to the iBook considering its appearance and the fact that in the manga of Digimon Adventure, it is referred to by name as a PiBook. Several images of the screen of Izzy's computer also resemble the Mac OS. (In the second Digimon movie, all the computers featured Windows screen shots becase a different animation studio was used.)
 * During Anime North 2006, Jeff Nimoy, a writer for the English dub, claimed that he used the personalities of gay lovers for Izzy and Tentomon.