“Elementary particles are things even tinier than molecules and atoms. We know that there exist gauge bosons, leptons, and quarks. There are also hadrons which are made when antiparticles or quarks gather, but, well, they're all divided into a few general categories. These elementary particles make up the world.”

“However,” said Kakine in a soft voice, “That kind of common knowledge does not apply to my Dark Matter!”
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“The Dark Matter I create is matter that does not exist in this world. It’s not matter that hasn't yet been discovered, nor matter that theoretically exists, but rather matter which undeniably does not exist.”
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This pair of black wings, Kakine had seen it before, and knew what it was.
The elementary particles that didn’t exist in this world, Dark Matter.

Toaru Majutsu no Index vol.15 ch.5 pt.3,4