Leader X, also known as Sosai X, is the supreme and mysterious leader of the terrorist organization Galactor. An alien entity from the planet Selectoru, Leader X traveled millions of light years to reach Earth with the intent of conquering the planet. In the movie, his arrival and the creation of his primary agent are depicted in newly animated footage. To serve as his field commander, he took a pair of male and female twins and fused them into a single, genetically engineered mutant known as Berg Katse, who then leads Galactor's day to day operations. Leader X's background reveals him to be an artificial intelligence, possessing a male personality but being technically neuter in form. His motivations are rooted in his alien origin, seeking to subjugate Earth for his own race or purposes, viewing humanity as an obstacle to be eliminated. He transforms Galactor from a smaller criminal organization into a massive, technologically advanced global terrorist force. In the story, he serves as the ultimate antagonist, the unseen puppet master whose commands drive the conflict against the Science Ninja Team. His key relationship is with Berg Katse, whom he created and treats as a subordinate and surrogate, though their bond is one of control and purpose rather than genuine affection. Leader X's development is minimal within the movie itself, as he remains a distant, almost mythical figure, but his nature is established as a persistent and adaptative threat, with pieces of his consciousness surviving later defeats. Notable abilities include his advanced alien intellect, mastery of genetic engineering and robotics, and the capacity to direct Galactor's global operations from the shadows. He is portrayed as a cold, calculating, and ruthless intelligence, utterly committed to his goal of world domination.