He was the lead developer within R.R.D.'s Ener-D Reactor who was killed in the Zero Reverse effect. His leading position of R.R.D. was due to the fact that he was the leader behind the research into the "Planetary Particle", which 17 years ago was the particle needed for the development of the Ener-D technology.
This research consisted on the planetary gear which is one that is able to bind particles to others. Dr. Fudo named his son, Yusei Fudo, in honor of this particle, which is named Yuusei Ryuushi, as he wanted his son to be able to bond people together.
Soon after, Roman overrides the system leading to the Zero Reverse incident. Dr. Fudo's last act is to save his infant son, Yusei, by ejecting him from the Ener-D development area in an escape capsule immediately before he is killed by the negative energy explosion. (In the English version, he had disappeared before the Ener-D reactor began to malfunction, releasing all that negative energy).
Following his death during the Zero Reverse, Dr. Fudo's spirit remained in the Old Ener-D, and appeared several times to Yusei, helping and inspiring him to not give up. He has the ability to somehow manipulate time, as shown in Episode 117, when he sends Yusei back to his own time. In the same episode, he shows that he is also knowledgable of what the Divine Temple is.
Yu-Gi-Oh! 5D's Manga
Yu-Gi-Oh! 5D's (Anime)
Dark Signers arc
Rex Goodwin mentions him just before Yusei and the others are about to travel to Satellite aboard a helicopter. He tells Yusei that he and Roman Goodwin, Rex's older brother, were Dr. Fudo's head assistants.
Later on Roman tells Yusei and the others that Professor Fudo wanted to cancel the Ener-D research, as he already suspected that its rotation was quite unstable. Furthermore, he realized that there might be an accident (as it happened, he was right). However, its proposed cancellation was rejected by the City, causing Professor Fudo to be removed from the project and replaced by Roman.
Later on Mina Simington reveals to the Signers that Yusei's father entrusted the "Red Dragon Archfiend", "Stardust Dragon" and "Black Rose Dragon" cards to Goodwin, so that their correspondent Signer could seal the control units of the Ener-D Reactor. She says that he obtained them from Roman, immediately after he was released from the project. When Roman showed the four dragon monsters to Professor Fudo, including Ancient Fairy Dragon, Dr. Fudo took them and ran. However, he was attacked during his flight, so he dropped Ancient Fairy Dragon, similarly to how Uru dragged the dragon down with it as the spider was sealed in the Nazca Lines.
Dr. Fudo makes a brief appearance in the Underworld during the events of Episode 58 after Yusei falls into the light of the Original Ener-D Reactor. He saves Yusei, and brings him to a river in the underworld. (This is thought to be Sanzu No Kawa, a river that is thought to be the gate to the underworld in Japanese Mythology.) There, he tells Yusei something important, while fading away. Yusei tries in vain to follow and talk to him some more. Unfortunately, his father disappears, and Yusei returns to the Ener-D Reactor, unconscious, though he quickly awakens.
Later, in Episode 117, he makes a brief appearance as Yusei and Bruno travel through Dimensions using Infinity. There, he talks about how Ener-D destroyed the world, before sending them back to their time. Later at the end of that episode, Yusei came to a realization about his father.
In episode 128 Yusei stated that Dr. Fudo might still be alive, but trapped inside the Ener-D/Divine Temple.
Ark Cradle arc
He appears in Episode 138 when Yusei decides to risk his life in order to prevent the Divine Temple from destroying New Domino City.
In Episode 150, Yusei falls off his Yusei Go during his duel with Z-one. A beam of light from the Ener-D reactor stretches out to him as he falls. Inside a void of space Dr. Fudo appears before his son, encouraging him to continue fighting. Also physically striking him to get him back on his feet. Dr. Fudo tells Yusei that as the Planetary Gear does, Yusei connects the hearts and feelings of others, and that is his role now. As Yusei gets up Dr. Fudo vanishes, saying this is the last time he can appear to Yusei. Yusei reappears in the real world, still falling, when the Yusei Go drives down of its own accord to catch him. Yusei attributes this act to his father and thanks him before continuing the duel.
Team 5D's Future
During Jack and Yusei's duel, Yusei mentions his father and brings his friends and himself to tears.
- Japanese : Daisuke Hosomi
- English : Wayne Grayson
all Information on Dr. Fudo came from http://yugioh.wikia.com/wiki/Dr._Fudo