It is set in the distant future, where a man known as JP takes on great risks for the chance of winning the titular underground race.

JP initially turns down the money but a crowd of reporters storms the hospital room where JP learns that he has been voted by popular demand for the Redline following the dropout of two qualifiers due to the revelation of the race's location being on Roboworld — a planet dominated by militant zealot cyborgs whose President has threatened to hang all involved with the Redline mothership if it appears out of hyperspace over their planet.

The racers prepare for Redline by camping out on EUЯPSS, a demilitarized moon of Roboworld occupied by refugees in the M-3 Nebula Federation.

Volton reminds the racers any Redline event will be repelled by the army and police before retrieving Deyzuna and leaving the damaged restaurant.

Fireworks celebrations and bookmaker agent desks break out on Roboworld despite the threats from the military, and are raided by deadly android police robots.

Miners on Roboworld use their power suits to sabotage the military base's power station while the Race Commission hires Earth-native racing partners Lynchman and Johnny Boya to sabotage an Orbital Disintegration Cannon, which Secretary of Defense Titan plans to use to destroy the Redline mothership the instant it comes out of hyperspace.

He is attacked by mobsters for his decision but is saved by Old Man Mole, who discovered Frisbee's sabotage, and kills the mob boss and his lackeys.

As the racers rest at the end of the track amidst the ruins of Roboworld, JP and Sonoshee float back down to the ground kissing and declaring their love for each other.

[4] Redline was initially meant to premiere at the 2009 Annecy International Animated Film Festival and follow Summer Wars, Mai Mai Miracle, and Yona Yona Penguin as the fourth and final feature film Madhouse planned to release between summer 2009 and spring 2010.

Although Maughan says some may dislike its techno soundtrack and "minimal plot," he calls Redline "the most insanely exciting, visually exhilarating anime film you've seen in decades.

"[23] Nicolas Penedo of the French magazine Animeland describes it as the "Paris-Dakar revisited à la Ōban Star-Racers",[24] a remake of Hanna-Barbera Wacky Races with arts inspired from Jack Kirby comics and know-how, rhythm and energy inherent of the best Japanese anime movies.

[25] The reviewer praises the animation quality as breathtaking,[26] and declares that Takeshi Koike made an homage to comics and films of the 70s and 80s.

Bellette describes it as a "truly out of this world experience", "Speed Racer on crack" and praised the supporting characters for being memorable and the background galaxy made of different races and creeds to be very solid.

[27] Martin expresses that "it feels like every centimeter of every frame is filled with some kind of kinetic color or action or bit of business, making it an experience that is sure to overload the senses" and asserts that writer Katsuhito Ishii succeeds at making a feature-length anime as insane as his film Funky Forest.

[28] Jon Liang of UK Anime Network comments that "A sense of the cool and outrageous is seeped into every pore of the design, ... exaggerated is an understatement here", and notes that the film's "cinema-quality smooth animation" makes "even the most alien of things move naturally and the sense of speed that is often achieved is frequently mind-blowing."

He remarks that "the visuals and over-the-top action will most likely overload sensitive brain cells," but concludes by calling Redline "an incredibly exciting cinematic experience that doesn't take itself at all seriously.