Reideen

Saiga is an ordinary high school student with a knack for math. His quiet life is upended when his family learns that his father's remains have been found. His father, a well-known archaeologist, vanished years ago during an expedition. Among his belongings were notes and artifacts that the family is asked to identify near a famous triangular mountain in Japan-sometimes called "Japan's pyramid"-which some believe was artificially constructed. When a meteor crashes to Earth, it releases a hostile robotic creature that wreaks havoc, endangering Saiga. In the chaos, a strange bracelet from his father's research activates, fusing him with an ancient robot buried inside the pyramid. According to inscriptions, this robot is called Reideen. Now, Saiga and his newfound guardian, Reideen, must stand against the alien menace descending from the sky.