The Fifth was for himself.
His cultivation had reached a plateau and he needed astronomical resources to advance.
If he one-sidedly consumed Maya's energies, he could indeed advance, but he did not want that.
Leaving aside the fact that he was a sucker for a pretty face, weakening Maya for his advancement was plain stupid.
The other eight did not know of his existence.
If Maya suddenly lost a bunch of cultivation, they would surround her like vultures.
He might be able to stay safe, but what about the rest? He did not have enough confidence to fight eight level 99 beings on his own.
He did not even know their abilities.
Going in blind was just asking for an ass-whooping.
And he was too lazy to put himself in such a situation. He did not have any desire to play the protagonist of some story.