The year is 20XX. Mysterious huge robots called "Giant Robo (GR)" started to appear all over the world and destroy cities. The earth was covered with fear. And their next target is Japan! The hero of this animation Daisaku Kusama, who works in a diving shop, encounters a mysterious girl, simply called V who leads him to make a contract with an enormous robot "Giant Robo 1 (GR1)" at the ancient ruins (Minami Yonaguni Island) in Okinawa. He made a contract with UNISOM (good guys) and was approved to be a commander of GR1. Thus his battle has begun against GRO (bad guys) and creates a lot of dramas. Before long, Giant Robo of the 21st century will ask the world the true meaning of its power. (Source: AniDB)

Around the the 37th year of the Meiji Era (1904), in the midst of the Russo-Japanese war, the small Japanese army, in need of assistance, uses its special flying (thanks to a benevolent demon) ship, the Amanohara, to attack Russia's major base at Port Arthur (Lushun). Umakai Shintaro, a Russian diplomat originally from Japan, defects and goes to Sapporo to teach at a girls academy. However, that girls academy is not typical—it is on board the Amanohara, and the five girls Shintaro teaches are known as the Raimu Unit—girls with the ability to summon powerful beings to fight for them. Shintaro eventually becomes their teacher and general in battle, and so the six embark on a weird and excessively erotic journey, as Shintaro helps the girls overcome their weaknesses, become stronger for the final stand at Lushun, and also understand the motives of the "Russian Spiritual Corps" that assist the opponent, which, unfortunately, has one member whom Shintaro knew well... (Source: ANN)

With the battleship Amanohara seriously damaged and in need of repair, it lands on an island where a Gogyou festival has just begun. Shintaro Umakai and his five female students, known as Raimu Unit, enjoy a period of peace on the island. However, the enemy still pursues them. Umakai and his unit deal with the enemy while the five girls try to draw his attention. (Source: ANN)