Medical-nin

Medical-nin (医療忍, Iryō-nin ) are ninja specialized in medicine and medical care or ninjutsu oriented to heal people. Becoming a medical ninja-nin requires high intelligence and advanced chakra control . Some medics like Sakura Uchiha and Tsunade are also versed in the elaboration of medicines with medical plants and herbs. The rules of medicine declare that medical-nin are not fighting shinobi but ninja of support, and they are obligated to stay in the rear to supply care for the reason that if there are injured people, then there would be nobody to heal the other members of their team . During the Second Shinobi World War , Tsunade advocated the inclusion of a medical-nin on high ranking missions to increase the success rate of the mission and overall survival rate of the squad. However, this idea was dismissed by the Third Hokage because of the amount of time it takes to train them .

Not every medical-nin is proficient in medical ninjutsu because of the high difficulty involved. The Mystical Palm Technique - a technique used to accelerate the body's natural healing process and that requires advanced chakra control, is the universal and most basic form of medical ninjutsu . For this reason, ninja shown to be able to master this technique are considered medical-nin and assigned to teams, thus becoming field medical-nin. They carry supplies in their ninja pouches with medical supplies like first-aid equipment and anesthetics . Other ninja that center their training in more advanced medical ninjutsu are called be part of the Medic Corps, who are professional doctors and medics that develop medicine, research about diseases and ninjutsu focused on healing . The Medic Corps are gathered in the Konoha Hospital , a facility where the personnel have materials at their disposal to help the medical needs of patients and they work here full-time. The personnel of the Hospital require skill to treat more serious injuries such as the Healing Resuscitation Regeneration Technique , which uses a portion of the patient's own body as a medium to help the healing process; or to perform surgeries and autpsies . Field medic-ninjas indicated for battle don't have enough knowledge to be part of the Medic Corps.

Inside the Medic Corps, there are also ninja versed in the knowledge of veterinary medicine for the treatment of ninken . Hana Inuzuka is a veterinary medical-nin .

In the present, Sakura Uchiha is the best medical-nin in the world, being able to surpass her master . She is a teacher of medical ninjutsu for the new generation of genin interested in becoming medical-nin. She dedicates a room inside her Hospital for teaching classes in the art of chakra control and the subsequent knowledge of healing techniques .

The knowledge of a medical-nin can be used for a variety of purposes. Chiyo , in the past, used her medicinal knowledge to create deadly poisons. However, her efforts were often counteracted by Tsunade, one of the most famed medical-nin in the world. Sasori used the knowledge passed down from her grandmother in the elaboration of lethal poisons, but Sakura Uchiha, hailed as the best medical-nin, was able to create an antidote in only a few hours . Sakura also spend time in the training of medical-nin specialized in the mind in order to open her Therapy Center after the war . Only two medical-nin, Tsunade and Sakura Uchiha, can apply the chakra control used in medical ninjutsu for chakra enhanced strength and be able to participate in battles.

According to Madara Uchiha , the First Hokage, Hashirama Senju , was also able to use medical ninjutsu with such skill that he could heal himself instantly without the need of performing hand seals; Madara included that Tsunade, who is heralded as one of the greatest medical-nin in the world, pales in comparison - something Tsunade initially herself admits - but after seeing her Ninja Art Creation Rebirth - Strength of a Hundred Technique , Madara deemed Tsunade's healing abilities similar to that of her grandfather's.

Tsunade has also been credited with creating the official system of the medical ninja along with which she created laws that her students and other medical-nin alike, should abide by. The four rules that govern medical-nin are:

- First clause (第一項, Daiikkō ): " No medic ninja shall ever stop medical treatment until the lives of their party members have come to an end. " (「医療忍者は決して隊員の命尽きるまで治療を諦めてはならない」, "Iryō ninja wa kesshite taiin no inochi tsukeru made chiryō o akiramete wa naranai." )
- Second clause (第二項, Dainikō ): " No medic ninja shall ever stand on the front lines. " (「医療忍者は決して最前線に立ってはならない」, "Iryō ninja wa kesshite saizensen ni tatte wa naranai." )
- Third clause (第三項, Daisankō ): " No medic ninja shall ever die until they are the last of their platoon. " (「医療忍者は決して小隊の中で最後まで死んではならない」, "Iryō ninja wa kesshite shōtai no naka de saigo made shinde wa naranai." )
- Fourth clause (第四項, Daiyonkō ): " Only those medic ninja who have mastered the Strength of a Hundred Technique of the ninja art Creation Rebirth are permitted to discard the above-mentioned laws. " (「忍法創造再生の百豪の術を極めし医療忍者のみ 上記の掟を破棄できる」, "Ninpō Sōzō Saisei no Byakugō no Jutsu o kiwameshi iryō ninja nomi, jōki no okite o haki dekiru." )

Since Tsunade and Sakura Haruno are currently the only ones who are able to use the Ninja Art Creation Rebirth — Strength of a Hundred Technique, this effectively means that they are the only medical-nin allowed to break the above rules.