Every week, an intergalactic game show known as "Galaxy Warriors" would send a contestant down to Earth. Their mission was simple: they had to get the Ninja Power Stars from the Ninja Steel Rangers and entertain the audience at the same time. Sometimes, a contestant would be defeated by the Rangers, but if most of the audience loved the contestant's performance, the host would "gigantify" the monster. Galvanax, the champion of Galaxy Warriors, wanted the Ninja Power Stars for himself.
This week, the contestant was introduced and sent to get the Ninja Power Stars, but something happened. A red portal appeared inside the ship. Some of the Kudabots, robots that served as staff in Galaxy Warriors, went to check out the portal that appeared inside the ship, but then someone appeared. He looked like the Red Ninja Steel Ranger, except that instead of red, his suit was black with some bright red lines on it. He was known as Akuroninja, an evil ranger from a dimension known as Earth-4. Akuroninja was the supreme leader of all of Earth-4, but this made him bored. Akuroninja then created equipment that allowed him to travel to other dimensions. He would also send his enforcers to other dimensions. Galvanax, the champion, approached Akuroninja, since Ripcon, one of Galvanax's soldiers, had been destroyed by the Ninja Fusion Megazord.
Galvanax had already seen someone who looked like him already, except instead of an intergalactic game show champion, his lookalike was an evil warlord. Galvanax also noticed that Akuroninja reminded himself of another black ranger whose design looked similar to the Red Ninja Steel Ranger.
"Who are you?" Galvanax asked.
Akuroninja said "I am the ninja of evil: Akuroninja."
Meanwhile, someone who looked similar to Akuroninja was observing something. Instead of black with some red armor, this ranger was light grey. He was known as Anti-Kuroninja, whose archenemy was Kuroninja. Anti-Kuroninja was currently allied with the Cyberninja Tech Company, who wanted him to be their leader. Anti-Kuroninja had access to Cyberninjas, very strong robotic ninjas created by fusing the soul of a ninja with a robot body. Anti-Kuroninja's Cyberninjas were destroyed many times by his archenemy Kuroninja, and sometimes, Shuriken Sentai Ninninger, now with a green ranger.
Anti-Kuroninja was currently focused on the Ninningers. Although Anti-Kuroninja was very calm and good at creating strategies to take down his enemies, he was obsessed with two things related to the Ninningers. The first one was the Midoninger Shuriken. He knew it was very powerful, but he only used it once. Kuroninja, however, teamed up with the Ninningers and their lookalikes, the Ninja Steel Rangers, to get the Midoninger Shuriken back, even though Anti-Kuroninja's plan was to get the Ninningers and Ninja Steel Rangers to fight each other. Anti-Kuroninja also had an obsession with Shironinger for some reason, and recently, most of Anti-Kuroninja's plans involved separating Shironinger from the rest of the Ninningers so that Anti-Kuroninja could capture Shironinger. Even though Kuroninja was the opposite of Anti-Kuroninja and tried to avoid Shironinger, he would still protect her from Anti-Kuroninja.
Anyway, Anti-Kuroninja had been defeated many times by Kuroninja, that he needed help. He then remembered that there were other Kuroninjas from other dimensions who were evil. However, the only one Anti-Kuroninja could think of was Akuroninja, who was known for breaking alliances with other villains. That was when Anti-Kuroninja looked at one of the Cyberninjas and remembered that there was an evil Kuroninja from Earth-9, a universe conquered by an evil empire, just like Earth-4. This evil empire, however, was being opposed by a rebellion, especially nine ultimate saviours. Anti-Kuroninja knew that Kuroninja had a weakness for a certain green ranger from this universe, but he also knew about Cyber Kuroninja, who was from this dimension. Anti-Kuroninja summoned Cyber Kuroninja, who appeared from a portal. Cyber Kuroninja decided to ally with Anti-Kuroninja.