Sairagin is a giant rhino-like alien child (make that student) who was used as a Silver Imperial Army Monster of the Silver Imperial Army Zone.
She is voiced by Chika Sakamoto who later voiced Wameikle from 2008 TV series called Engine Sentai Go-Onger.
Sairagin is a being from a race of giant aliens from a planet called Saira (because on home planet its only natural, but to the other alien he's a bit big to the smaller ones). So in order to keep the Fiveman occupied and to stop their mecha Dongoros bribed Sairagin for 5 dolyens just to come to Earth to cause a ruckus on it. As this goes on Dogoros plants a giant tack in the ground (which also cost about 10,000,000 dolyen) as it disables one of the Land Gamma's tires. After that Kazumi decides to check on this "Galactic Warrior" because she feels that Sairagin isn't their typical Zone monster while Ken and the other Hoshikawa siblings fixed the Land Gamma.
When Kazumi arrived at the giant Sairagin she was then attacked by him as it used his giant pencils to attack her. As this goes Sairagin accidentally impaled his foot on one of his sharpened pencil as he cried in pain. Turns out he's just a child so she used Fumiya's linguistic abilities to talk to Sairagin. She then finds out about Dongoros' bribery and his own problem which is having a hard time at school as he failed in its math classes due to not fully understanding in simple arithmetic. So Kazumi makes a deal with Sairagin if she helps him remove the pencil from his foot she'll teach him about math. So he agreed to this kind of deal as they managed to removed the pencil from the foot and then both Kazumi and Fumiya began tutoring Sairagin by using its pencils as a visual to teach him how to add and subtract.
However it didn't went unnoticed when Dongoros saw what Sairagin is doing. Turns out he learning about math instead of doing destruction on the planet. So he brought the 6th Gorlin to absorb Sairagin into an obedient genetic and not to mention an army Vulgooru to prevent the Fiveman from getting in his way. So with the repairs fix on the Land Gamma they formed the FiveRobo and defend the alien as FivePink and Black teach Sairagin about addition while attacking the Zone's Vulgooru and holding off the blank Gorlin last for subtraction. Once the lesson has been learned for Sairagin, FiveRobo destroyed the blank Gorlin to prevent it from absorbing the child.
Happy with its lesson learned, Kazumi writes a huge "100" and also drew a heart shaped on Sairagin's tusk, with this done Sairagin is happily leaving the planet with its new math skills.
When the Galactic Wolf Gunther tries to pursue FiveRobo to test out his new Star Five mecha, he fights Sairagin on planet Saira in hopes to get information out of him. After a brief battle, the giant informs the warrior of Fiveman's location on Earth, worrying about the team's safety in the process.
Silver Imperial Army Zone