Humans don't need the gods...they need us...we are the greatest species in existence and Marisa is the greatest being of our species...
Okay, technically Junko too, but she's more of an it after purifying herself
Technically Youkais and Gods were created by the humans fears, and in the image of the imagination of ancient people. For them to preserve their existence, they use the humans they locked in Gensokyo to keep feeding off of their fears.
That is the correct answer, o' child of man.A god can be killed...Not by another god, not by magic...But by a human, certainly.It's precisely because you're human that you can do it...Aah......This is what makes Gensokyo so fascinating...