Synopsis
Saiga, a high school student gifted in mathematics, has his everyday life interrupted when news arrives that his father's remains have been found. His father, a famous archaeologist and researcher who went missing years ago during an excavation, left behind notes and artifacts that must be identified by the family near a unique triangular mountain in Japan, known as "Japan's pyramid." Some people theorize that this pyramid was built by human hands. Suddenly, a meteor carrying an unusual robotic organism crashes down, endangering Saiga's safety. This event triggers a mysterious bracelet from his father's leftover research, merging him with an ancient robot buried within the pyramid—inscriptions indicate that this robot is named Reideen. Now, Saiga and the guardian Reideen must face an unknown alien threat descending from the sky.
