Though poison-sprite fairies appeared to be a separate race, they were fundamentally a part of the Demon Race, just another branch of it. The people of the Demon Race longed for peace and hoped for love and the status quo; they merely wished to live peacefully within their homeland. But the poison sprites demanded a life in a beloved place, dissatisfied with the status quo, always looking to invade others' lands.
However, they had long been unable to intrude into the territory of the Demon Race because their abilities were not seen as powerful by the Demon Race. It was only now that their reaction abilities had been repeatedly strengthened by the Fire Emperor, causing their numbers to dramatically increase and become a formidable threat.
When it really came down to comparing abilities, they were not at all on par; they seemed like nothing but a minor race, even just a family, driven solely by tremendous ambition and exploited by the Fire Emperor.