This particular technique, or rather, condition is inherent to Mukūrō due to his possession of the Curse of the Wallowing Vulture. Knowing full well that the curse is a product of Kaguya Ōtsutsuki, those who bear the curse also react uniquely to those who possess Tailed Beast chakra — in other words, fragments of the Ten-Tails and Kaguya herself. In this case, the reaction appears to cause a physical embellishment on Mukūrō's body in the form of a hole-like tattoo on his neck, the pain of which can also be briefly felt by Mukūrō. While it grants no actual attributes, it can be used by the man to sense the presence of an incoming Tailed Beast, even if its presence is hidden through a layer of sealing techniques.