>>8630938
It's an accessory.

I'm using these ones:
ボーン入りち○ぽモデルfeat.たいぷはてな
ボーン入りち○ぽモデルfeat.たいぷはてなフリーカラー+NPR
ボーン入りち◯こ+舌
子宮&ボーン入りち〇こv2

Basically a penis with bones in it, so it can be edited in ShapeAnimator, like increasing proportions and adding curves.

There is also "ONN" penis for shotas.