Three kids' robots built for a school competition become real weapons overnight. Professor Mizuki doesn't ask permission, he just takes what they made and repurposes it for war. That collision between innocent creation and forced militarization is the actual story here, not the alien invasion playing in the background. You're watching teenagers process the moment their passion project becomes a tool, their ingenuity weaponized without consent. The mecha itself is secondary. The cost of being useful when the world needs soldiers is everything.

Three talented students at a technical high school, Daisaku, Tetsuya and Hotaru, build robots for a school competition and win an award for them. At the same time, the Derinja, an evil race bent on ruling all of space, turns its ambitions toward Earth. To fight back, Hotaru's father, Professor Mizuki, takes the three robots and converts them for combat. The machines can join together into a single giant, the super robot Albegas, and Earth's hopes rest on it. Hotaru is the professor's gifted daughter, Daisaku is a cheerful martial artist, and Tetsuya is a cool, tough loner. Together they pilot the combined robot in this 1983 mecha series.