Nezbitt

Nesbitt, known as Soichiro Ota in the Japanese version, was the technical expert at KaibaCorp and a member of the Big Five.

KaibaCorp
Nesbitt worked as at KaibaCorp, where he oversaw the military factories. Nesbitt, along 4 other KaibaCorp employees formed a group known as the Big Five.

Seto Kaiba, the adoptive son of the head of KaibaCorp, Gozaburo Kaiba, convinces the Big Five that Gozaburo is mistreating them and he'll help restore them to their former power. The Big Five agree, and thus buy 49% of KaibaCorp. Combined with 2% that Gozaburo had previously given to Seto for a test to prove his business skill, the Big Five vote out Gozaburo and vote in Seto as the president of the company.

However, Seto quickly backs out on their deal, stripping them of their power and leaving the Big Five little more than figureheads and consultants. Seto ordered Nesbitt to destroy his lab and had him build the Duel Tower in its place. Nesbitt was furious over his technological genius being used for games, and has vowed revenge.

Duelist Kingdom
Furious over their betrayal, the Big Five strike a deal with the president of Industrial Illusions, Maximillion Pegasus in an attempt to overthrow Seto. If Pegasus defeats Seto and Yugi Muto in duels, then they will use their 49% to vote Pegasus into power of the company by kidnapping Mokuba Kaiba, who has been entrusted with the security codes to the two percent the Big Five need.

The Big Five and Pegasus' plan fails, after Pegasus is defeated by Yugi. In the manga, Seto fires them for their betrayal.

Legendary Heroes
In the anime, the Big Five avoid being fired, by making excuses and offering Seto his complete virtual reality game as a peace offering.

Eager to try out the virtual reality game, Kaiba refrains from immediately firing them and enters the virtual world. The Big Five trap Kaiba in the virtual reality.

However Kaiba is rescued by Mokuba, Yugi, Joey Wheeler, and Mai Valentine. The Big Five reprogram the game and set the "Mythic Dragon" as the final boss. However it is defeated by Yugi and Kaiba's "Dragon Master Knight".

Virtual Realm
After losing in Legendary Heroes, the Big Five got trapped in the virtual world, instead of Kaiba. Here they meet up with Noah Kaiba. Having Seto as a common enemy, they make plans to get revenge.

During the Battle City tournament, Noah has the KaibaCorp blimp sucked into an undersea fortress, where the virtual world's main servers are. They force Seto and Mokuba Kaiba, along with Yugi and his friends into the virtual world again. Using an altered set of Duel Monsters rules, involving Deck Masters, the Big Five duel their enemies in the hopes of stealing their bodies to escape the virtual reality.

Nesbitt took the form of "Robotic Knight" to Duel Duke Devlin, Serenity Wheeler and Tristan Taylor. He initially planned on dueling them 1 at a time, starting with Serenity, but Duke and Tristan talked him into in a three-on-one Duel. Since Tristan and Serenity had little knowledge of dueling, Nesbitt was sure he'd win easily.

With Nesbitt easily lowering Serenity's Life Points, as she doesn't know how to play, Tristan worries and uses his Deck Master to protect Serenity from an attack from Nesbitt. This causes Tristan to lose and Nesbitt has him ejected from the arena.

Nesbitt plays his Deck Master, himself, onto the field and combines himself with his "Machine King" to form his new Deck Master "Perfect Machine King". Due to "Clockwork Night", his opponent's monsters were all Machine-Type, therefore powering-up "Perfect Machine King". However Serenity manages to Summon "St. Joan" and she and Duke, with the help of Tristan's last card manage to raise the ATK of "St. Joan" equal to "Perfect Machine King's" ATK and defeat it, hence defeating Nesbitt. Since Nesbitt at least managed to beat Tristan, he steals his body, leaving Tristan's mind in the body of an "Acrobat Monkey".

In this form, Nesbitt attacks Kaiba with a kendo stick, but is attacked by robot Tristan. He kidnaps Mokuba, for Noah, and escapes on a motorcycle. Before leaving to the real word, the other members of the Big Five protest that Nesbitt didn't rightfully win Tristan's body, so Noah allows to five of them to share it in order to Duel Yugi Muto. Should they win, they would all get their freedom.

The Big Five face Yugi and Joey Wheeler, using Tristan's body. The 5, each switch control and Deck Master throughout the Duel. Nesbitt only takes full control for 1 turn, where he uses "Heavy Storm" to destroy Yugi's "Mirror Force", unknowingly raising the ATK of "Des Volstgalph" in the process, he then attacks "Des Volstgalph" with "Machine King", only to have "Machine King" destroyed. Towards the end of the Duel, the Big Five uses "Dragon Revival Ritual" to combine their Deck Masters into the "Mythic Dragon" again. The dragon is destroyed by Yugi and Joey's "Mirage Knight", but the Big 5 use "A Deal with Dark Ruler" to make "Berserk Dragon" their Deck Master. However it is destroyed by "Dark Magician Knight", costing them the Duel.

Noah refused to give the Big Five any more chances after that and left them trapped in the Virtual World. They have not been seen since. Later, when the virtual world was destroyed, everyone inside it at the time was destroyed with it, including the Big Five.

Deck
Nesbitt uses a Machine Deck centering on "Machine King" and boosting its strength with "Clockwork Night". His Deck Master, "Robotic Knight's" special ability is Final Artillery, which deals 500 damage to his opponent each time he discards a Machine-Type monster.