"Crystal Triangle" is a 1987 anime OVA set in a world where ancient artifacts and mystical powers intertwine with modern-day intrigue. The narrative centers on a mysterious artifact known as the Crystal Triangle, believed to hold immense power capable of altering the course of history. The story begins with the theft of the artifact from a museum in Tokyo, setting off a chain of events that draws in various factions, each with their own motives for possessing it.

The protagonist, Ryo Takagi, is a young archaeologist who becomes entangled in the search for the Crystal Triangle after his mentor is murdered during the theft. Ryo is joined by Karen, a journalist investigating the artifact's significance, and Shin, a skilled martial artist with a personal vendetta against those seeking the Triangle. Together, they uncover a conspiracy involving a secret society known as the Black Lodge, which seeks to use the artifact to resurrect an ancient civilization and gain dominion over the world.

As the trio delves deeper into the mystery, they encounter a series of challenges, including rival treasure hunters, supernatural forces, and the Black Lodge's elite operatives. The story explores themes of power, greed, and the consequences of tampering with ancient relics. The Crystal Triangle itself is revealed to be a key to a lost civilization's technology, capable of unleashing catastrophic events if misused.

The plot is driven by a mix of action, suspense, and historical intrigue, with the characters navigating a web of alliances and betrayals. Ryo's determination to protect the artifact from falling into the wrong hands forms the emotional core of the narrative, while Karen's investigative skills and Shin's combat prowess provide the means to overcome obstacles. The Black Lodge, led by the enigmatic and ruthless Dr. Kano, serves as the primary antagonist, with its members employing both scientific and occult methods to achieve their goals.

The OVA concludes with a climactic confrontation at the Black Lodge's hidden base, where the true nature of the Crystal Triangle is revealed. The resolution hinges on the characters' ability to balance their personal motivations with the greater good, ultimately deciding the fate of the artifact and the world. "Crystal Triangle" blends historical mystery with science fiction elements, creating a narrative that is both engaging and thought-provoking.