Sakon and Ukon's unnamed kekkei genkai gives them the unique ability to break their bodies down to a molecular level. The two brothers usually use this ability to share the same body but can also use it to merge with the bodies of others and destroy the host's cells from the inside. When Sakon is in need of assistance, Ukon can bring out some of his body parts to aid Sakon in blocking or attacking. Ukon's arms and legs can emerge from those of Sakon's to increase the force and quantity to his physical attacks.
If needed, Ukon can separate from Sakon's body so that the two can attack independently. While this can be an effective way of double teaming an opponent, Ukon is not used to leaving Sakon's body and is much weaker when he does so. While within another's body, however, they are vulnerable to whatever injuries befall upon the host, in theory allowing the host to commit suicide to kill either of the brothers. After their separation, should any injury befall either of the brothers, they can merge with each other to heal. This way, their healing rate is much faster than that of a normal human's, though it depletes a large amount of chakra. If Sakon is the one to lay dormant for healing, Ukon will have trouble as he is not used to being the lead body.
After integrating Sakon and Ukon's DNA into himself, Kabuto gained access to this kekkei genkai.