Hikari no Senshi Daiyamondo Ai (1973)

On the trail of a ring of gem thieves "Weekly Japan" reporter Rai, Kotaru ends up in a battle against an evil that threatens all of Asia. Kotaru follows a lead to a gem trader Gen Kai Ryuu not realizing that Gen Kai Ryuu is the leader of the jewel thrives (and something far worse). Kotaru is captured by the gangsters and about to executed by Gen Kai Ryuu when the "King of Arabia" blue diamond begins to glow and a voice from the gem orders Gen Kai Ryuu to stop. A strange blue figure with diamonds for eyes comes out of the ring. He introduces himself as Diamond Eye. He breaks Kotaru's bonds and chases the gangsters into the street. As the gangster attempt to flee Diamond Eye hits them with twin beams from his eyes. The "Inner Soul Illumination Beam" (Gedou Shoshin Reiha Kôsen) reveals that these gangsters are in reality ancient evil beasts known as "Zensei Majin". When Gen Kai Ryuu tries to escape Diamond Eye reveals him be to King Cobra the leader of the Zensei Majin. After using the "Inner Soul Illumination Beam" Diamond Eye then says to the Zensei Majin, "Thine true form have I seen Zensei Majin ________" (filling the blank with its name) to which the monster replies "I've been exposed!" Thus begins Kotaru and Diamond Eye's: Warrior of Light's battle against the dark forces of the Zensei Majin.