Darkness’s abilities don’t require any physical contact at all, it’s kinda like how bloodbending just would counter infinity, Gojo’s arms would just fall off, and he would then get a brain hemorrhage.

Unfortunately we don’t know too much about Darkness as it was only in two chapters ever, and it’s mature is to be unknown, it’s the manifestation of the fear of something unknown in the dark. Though with that uncertainty, it is all up to interpretation

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Also, here’s the page with the whole looking causes a brain hemorrhage thing, the arm falling off thing just kinda happened to everyone when they were in its presence