Hiruko uses this technique through his Chimera Technique in order to forcibly extract the physical and spiritual energy of another ninja, even from a considerable distance. He can either absorb the chakra into the upper square of the mark on his left hand or his mouth. By using the latter, the technique's range is bigger as his mouth becomes like a giant chakra-suctioning vaccume. He is able to completely remove the victim's chakra, potentially causing death.
After using this ability, Hiruko is able to detect their natural elemental affinity, and then freely manipulate the victim's chakra element and perform ninjutsu of that element. This allows him to deconstruct and learn the abilities of his opponents, and he can presumably utilise all forms of nature transformation as a result.
When Hiruko tried to absorb Naruto's Wind Release: Rasenshuriken, he was unable to combine the shape and nature manipulation, and the technique fell apart.
The first sign in Kyūketsukō (吸穴孔), shares the same beginning with Kyūketsuki (吸血鬼), which means "vampire".