This onahole is an item from the demon world that is connected back to the succubus that owns it. Once you are inserted in it, you can't pull out due to it's magical power, and your defenceless genitals are at the mercy of the hungry succubus!?
In page 8, when he says "when the sage comes around, I'm sure he'll be able to get my penis out.", I'm not sure if he's using weird slang to say he'll try to take his dick out after he ejaculates and enters "sage mode", or if he's actually referring to a real sage in his world that can perhaps break the curse holding him in the wormhole.