An aquatic creature, Raiju invokes a Galapagos iguana and Crocodile in appearance and behavior. Broad shouldered, Raiju is heavily armored along its back and head. The "head" itself is a tripartite jaw that encases the creature's bioluminescent head for protection. Its feet are bent, enabling it to swim quicker through the water.
Raiju emerges from the Breach along with Scunner and Slattern to defend it from Gipsy Danger and Striker Eureka. When the Jaegers arrive to bomb the Breach, he proceeds to stalk the Jaegers from the darkness during their approach to the portal. Raiju assists Scunner in attacking Gipsy Danger, tearing its right arm from its body before Gipsy Danger can kill Scunner.
As Raiju circles around for a second attack, the Jaeger receives a warning from the Hong Kong Shatterdome which is monitoring the situation. Heeding the warning, Gipsy Danger's pilots angle the Jaeger's remaining GD6 Chain Sword so that Raiju runs itself onto the weapon. Gipsy Danger uses the sword and Raiju's own momentum to bisect the Kaiju, killing it.
After Striker Eureka detonates its thermonuclear payload, Gipsy Danger grabs one half of Raiju in order to use the Kaiju carcass to bypass the Breach's defenses. As the crippled Jaeger approaches the Breach, it is confronted by the severely wounded Slattern. In response, Gipsy Danger abandons Raiju's carcass in favor of using Slattern instead.
- Raiju's nickname during development was "Croc".
- According to Tendo Choi, Raiju was the fastest Kaiju on record prior to the appearance of Slattern.
- The appearance of Raiju, specifically its head, may be an homage to the Ultraman monsters, Gabora and Suppitol, who also have a protective false heads which they use to protect their real heads from their enemies.
- Raiju's name is a bit of a misnomer, as the Raiju of Japanese mythology was a creature with a broad range of appearances such as a wolf, cat, weasel, or fox. It was the companion of Raijin, the Shinto god of lightning.
- Raiju is a playable DLC character in Pacific Rim: The Video Game.
- Raiju is the heaviest Category IV Kaiju in Pacific Rim.