Yuka Inoue
A young girl that is one of Naoto's best friends. She helps maintain the "Junk" Computer she and the gang made together. Yuka provides the team spirit and constantly encourages her friends to do their best.
Ippei Baba
Naoto's other friend. Cheerful, he also helps monitor the computer when Naoto/Gridman fights. Ippei is also a talented artist. When Junk was first brought online, he used the painting program to design a superhero that would eventually become Gridman's body. He later used his skills, and hunger, to create the Barrier Shield.
Gridman
A 'policeman' of the Hyper World, a parallel world to the "Computer World" a world within all computers. While tracking down Kahn Digifer he encountered Naoto and chose him to merge with whenever battle must be done within the Computer world. To fight the larger and more powerful monsters, Gridman receives the upgrade program P-L6806OX to grow gigantic and battle against his foes. However, this massive power-up last only for a few minutes as it could overload Junk's system. When the power up begins to fade, a blue light on Gridman's head begins to blink as a warning. Naoto, Yuuka, and Ippei chat with Gridman over their computer by typing messages to him.
Junk
Computer built from used computers and other junk.
Daichi Sho
Naoto's younger brother.
Soichiro Sho
Naoto's father.
Michiko Sho
Naoto's mother.
Kana Baba
Ippei's younger sister.
Hiroshi Baba
Ippei's father.
Ayako Baba
Ippei's mother.
Hideyo Inoue
Yuka's father.
Yoshie Inoue
Yuka's mother.
Yoshihito Inoue
Yuka's elder brother.
Police Officer Koganemura
The police officer of the town in which Naoto lives.
Police Officer Amagasaki
The police officer who appeared instead of Koganemura.