Based on Mark Twain's famous book about the adventures of young orphan Huckleberry Finn.

Short specials from the DVDs.

After Leader X is seemingly destroyed for good at the end of Gatchaman II, a fragment of him that survived grows and mutates into Z. With the head of the Egobossler family, Count Egobossler (and his two subordinates Mechandol and Kempler), Z is bent on destroying the Earth, and the Science Ninja Team, once more. In the wake of Anderson's death, Dr.Nambu has become the new head of the ISO, while the team is now confined to the Gallatown (aka "G-Town") underwater base. Engineer Kamo is introduced, and after the New GodPhoenix is destroyed early on, the team receives the new Gatchaspartan as their mecha. The Gatchaspartan has a special mode as well, called Hypershoot, that can only be utilized by Ken (with his new "Gatchafencer" sword). As the series progresses, it is learned that the radiation exposure from constant use of the Hypershoot is slowly killing Ken, and that continued use would mean death. Meanwhile, Z plans to destroy the earth with an antimatter asteroid, codenamed "Poison Apple".

Ultra B (UB), is a small child from outer space who wears red sunglasses and has a star-shaped mole on his left cheek. It all began when UB's spaceship made an emergency landing in the forest. Lost and alone, UB was found by a young school boy named Michio. He was kind enough to take UB home for shelter, but only to learn that he was no ordinary child... but with supernatural powers! Thankful UB tries to use his special power to help Michio in trouble, but doesn’t mean that it always work out well. Especially, when UB sees a scary black cat, he loses control, and… (Source: TV Asahi)