Three talented students, Daisaku, Tetsuya, and Hotaru, attend a technical high school where they design and build award‑winning robots for a school competition. When the malevolent Derinja race, which seeks to dominate all of space, sets its sights on Earth, Hotaru’s father, Professor Mizuki, repurposes the trio’s creations for battle. The combined power of the three robots gives rise to the super robot Albegus.