Chikuzen Ooka or Johnson (in the English dub), is one of the Big Five from the Yu-Gi-Oh! anime. He is an expert lawyer and the legal expert of the Big Five. Johnson has thick black hair and glasses.
He was voiced by Shinichi Yashiro and dubbed in English by Andrew Paull, who also voices SCR-HD in Sonic Riders: Zero Gravity.
Johnson and the others were working for Gozaburo Kaiba at first, but then conspired with Kaiba to overthrow him. When Kaiba betrayed the Big Five, they joined forces with Pegasus J. Crawford, but he was defeated by Yugi Muto, so Kaiba fired them, but was imprisoned in the virtual world by them. However, their Five Headed Dragon was destroyed by Yugi and Seto Kaiba, imprisoning the Big Five in the virtual world.
They then joined forces with Noah Kaiba, entering his virtual world. As their bodies were destroyed, they needed to find new bodies to escape. Johnson dueled Joey and took the form of the Judge Man as his own deck master. He used a move called Clear the courtroom to destroy Joey's monsters and take off 500 life points for each monster. Though Joey was winning at first, Johnson MEANT for this to happen and when Joey played his gambling cards (Skull Dice, Graceful Dice and Gamble), Johnson cheated by making the dice land on 1 and the coin land on tails when Joey picked heads. Noah confronted Johnson for cheating and tried to delete him as punishment, but Joey convinced him to let the duel continue, as he wanted to defeat Johnson and knew he had a chance if played fair. Joey played Arduous Decision, which Johnson lost by picking the wrong card, allowing Joey to defeat him. Johnson was digitized.
Johnson returned alongside Gansley, Crump and Lector, attempting to steal the bodies of Joey, Serenity Wheeler and Duke Devlin, but failed. They then entered Taylor's body which Nesbitt had won and dueled Yugi and Joey. Johnson took control for one turn. After the Big Five were defeated, Noah gave them no more chances and deleted them.
In the 4Kids English dub, Noah imprisoned them each in a different corner of the virtual world. Johnson was killed along with Noah, Gozaburo and the other members of the Big Five when Noah destroyed the fortress with a satellite attack, deleting the virtual world and everyone inside it.
Johnson is perhaps the most evil and dishonest of the Big Five, as he would deceive the court in his career as a lawyer (once convincing a jury that a man who was afraid of water stole a boat). He also cheats in his duel against Joey and is the first to suggest the Big Five go back on their word to return Taylor's body if they lose. He treats the game of Duel Monsters as a trial, referring to summoning monsters as "calling to the stand" and attacking as arguments and how convincing they are. He considered Joey as an "inferior duelist" despite his defeat against him.
- Johnson was the only member of the Big Five to introduce himself in his human form, only taking his Deck Master form at the beginning of his duel with Joey.