Director of Kiriyama Heavy Industries and responsible for the creation of the Thunderclap Armas, he was a childhood friend of Reiji Moritsugu, whom he greatly respected for his ideals of justice. Over time, however, these ideals became twisted and warped, transforming him into a greedy, arrogant, and overconfident individual. His incarnations differ significantly: in the manga, he used the Katou Organization as mere guinea pigs to showcase the prowess of the Thunderclap, while in the anime, he initially forged an alliance with them. His insatiable greed for power led him to stage a coup d'état, granting him control over Japan and prompting him to attempt subduing the Katou Organization as well.
Kiriyama was a Factor, and to crush the remnants of JUDA after conquering Japan, he engaged in battle with them personally. He was defeated after being publicly unmasked as a ruthless dictator and one of the key figures behind the coup. Recovered by Katou and revived as a Machina-turned human thanks to Masaki Sugiwara, the fusion with his Machina drove Kiriyama completely insane. This fusion also sealed his fate; during a second confrontation with JUDA, he almost completely merged with his Machina and was obliterated. In his final moments, he reflected on how he truly admired Reiji's old ideals and wished to be a hero for him.
Eiji's Machina is Pretender, a unique machine capable of transforming from a fighter jet to a walking mecha at high speed, even mid-flight. Despite its unusual appearance, it boasts enormous mobility and firepower, equipped with numerous missile launchers and wireless Nerve-Crackers similar to those used by Deceive. For close combat, it wields a massive combat knife.
