Yin Body Type, also called Yin Pulse, refers to a physical condition that involves the function of the body and the circulation of Ki being irregular due to problem with the blood vessels.
The Yin Body Types are cases in which the body's veins are blocked in several places (from one to nine places). While in that condition the individual has many difficulties and malfunctions in the body and health problems. The health problems derive from the affected balance of the Simgichehon. Having blocked Yins means that the natural flow of the Ki (breath) is distorted and the Simgichehon is not balanced. No balance means malfunction of the body and, thus, health problems.
In contrast to the weak body of being a patient, curing the condition was rumored to make the affected person able to become stronger than regular people. Those people might be able to join or surpass the top of the Murim. Curing the Nine Yin Body Type is rumored to enable the patient to attain godlike techniques.
- Main article: Overhaul Rebirth
The reason why Overhaul Rebirth occurs is due to excessive Ki within the body. Thus, upon unblocking the Yins in the body by curing the Yin Body Type, the Ki running through the body can possibly cause the Overhaul Rebirth. Hence, according to Ju Sang-Sik, the Overhaul Rebirth appears more frequently at cases involving the Yin Body Type (or Pulse). Based on that, the reason why it occurred on Shi-Woon Yi was due to his Three Yin Body Type (or Third Pulse) condition. 
When Overhaul Rebirth occurs due to the curing of a Yin Body Type, like in Shi-Woon's cases, there is a high chance that the transformation caused by Overhaul Rebirth will start from the Vessel Tip, which refers to the blocked points of the Yin Body Type. 
Based on the results that Overhaul Rebirth brings and the rumors about the powers that someone with the Yin Body Type can attain after being cured, it is implied that the legend of the Yin Body Type patients is based on the occurrence of Overhaul Rebirth.
Since the most difficult condition is the Nine-Yin Body Type it can be implied that there are nine possible cases in total. Ranging from One-Yin Body Type to Nine-Yin Body Type. However, there are only two known types of Yin Body as of yet:
Nine-Yin Body TypeEdit
Nine-Yin Body Type or Ninth Pulse (Guumjiche), is a condition in which the vascular system of the body are blocked in nine places, stopping the circulation of Ki. It is believed that curing the disease would give one the ability to master godly techniques, unattainable by humans.
Three-Yin Body TypeEdit
Three-Yin Body Type or Third Pulse (Samjiche), is a condition where in the vascular system there are three places that have been blocked off. It can cause problems with blood pressure, making it difficult to be too active, causing chest tightness or fainting.
- Jang So-Sul: She has a Nine Yin Body Type. She was taken and healed from it to a certain extent, if not completely, by the Black Forest Defence.
- Shi-Woon Yi: He had the Three-Yin Body Type but was cured by the One Moon Divine Dan and the use of the Black Heaven and Earth Technique to help him contain the amount of Ki without destroying him.