Disclaimer: Obvious Infinite Stratos is not belong to me. This is just some of my thoughts on Ichika Orimura being the "only" male able to activate IS Cores.
Hope I'm not too bad on grammar...
IS shorted for Infinite Stratos, the perfect exoskeleton designed for outer space exploration but got laughed at when its mother published her creation after that it was recognized as super weapon with speed, offense and defense capable of wipe out any military when piloted by capable pilot. The person who created the main system, the basic hardware and firmware and power source of the IS in one package known as the Infinite Stratos Core was Tabane Shinonono, the Mother of IS Cores. Tabane Shinonono created 467 Cores that is what she said, most of them are shared by the world governments and large corporation or limited organizations.
Infinite Stratos is not for human male, so far no human male was able to activate one unit from 467 known Cores. Until one day when Ichika Orimura "accidentally or not" touched on the IS unit using for IS compatible test for female students at the facility using for high school entrance exams where he take the test for Aoetsu Private School, the high school neighbor to his house.
All hell break loss, for Ichika Orimura at least, few days after the planet shaking discovery of the first male capable of activate an IS he was shipped to Infinite Stratos Academy as know as ISA for his "protection" and education of controlling IS.
Governments, corporations and organizations tried to find out why Ichika Orimura can pilot IS. They known his sister Chifuyu Orimura is the first champion of the Mondo Grosso, the IS International Fighting Tournament designed to held every three years after the recognized of IS, the "Alaska Treaty" which states that IS will never be used for military combat and that existing IS technology must be equally distributed to all nations, to prevent any one nation from dominating the others, so piloting IS is a "sport" on face value. He was a friend with Houki Shinonono, the younger sister of Tabane Shinonono, when they was small. So what is his secret? He is special? He is mutant? He is hermaphrodite by genes like having XXY chromosome? Or his X is the same as his older sister X? No chance, if IS activate by X chromosome then any male would do fine. Or just on "whim" Tabane Shinonono added his exact molecular data to all the IS Cores data base for "creatures" can activate the Infinite Stratos? No one know how the IS Cores accepts its pilot.
No one know how he can pilot IS because no one except Tabane Shinonono know about the "firmware-hardware-power source" of the IS Cores. The IS Cores can accept external data but what data it release would be by its design. Maybe she make it that way for Ichika to be able to stand on equal term with her younger sister. May be it's the red thread of fate she created exclusive for her younger sister first crush, for her younger sister happy, for her future brother-in-law, may be it's her small redeem to her younger sister for she known she would take away the normal live of her little sister when she shown the population of the planet her creations.
But that would not stop the Governments, the Corp and Org to hope there would be the Second Male still somewhere out there. For now Ichika Orimura, the First Male, but would that make him the Only Male? They cannot, would not accept that easy.
All the male from top publish schools and private schools from elementary to university of all the nations all over the planet get to "touch-test" with an IS. Next would be students from less prestigious schools. It would take years to finish test half the human population exclude one for IS compatible. But it's a hope they can not let go of because he is the First Male. If he did not show up they would not bother for checking again. Now every new-born male would be tag for test in future.
Would there be the Second Male - the Beta - or the Third Male – the Gamma or even more male out there can activate IS Cores. Only Tabane Shinonono and those IS Cores themselves known if there would be any more human male other than Ichika Orimura can activate IS Cores.
Ichika Orimura would be happy because girls all around him or not? But for sure all those horny teenage chick want a piece of him, the Alpha Male, there would be no doubt a harem running after him around the campus. Was this a wrong decide from Tabane Shinonono for her younger sister Houki's happiness?
Because of Ichika Orimura from now on every human male or human hermaphrodite would need IS compatible test at least one in their life before their death.