Lightning speed would be "kaminari no hayasa."
The Japanese word for lightning is Inazuma.
Lightning=Inazuma
The speed of lightning is somewhere between that of light and sound which is why most scientists would agree that the speed of light and the speed of sound make a good comparison to that of lightning and electricity.
Hiraishin
雷 kaminari.
Lightning Flash in Japanese is 'Inazuma.'
Lightning. Because it is the speed of light.
The noun lightning itself (electrical discharge) is used as a noun adjunct, rather than an adjective, in such terms as lightning bolt or lightning rod. Only when the intent is to show great speed or quickness (lightning speed, lightning reflexes) is lightning an adjective.
A train couldn't go the speed of lightning. At least not with our technology.
Inazuma! ^_^
inazuma
inazuma