Katsuyu: Immense Network Healing

This technique is a combination between Tsunade and her slug summon Katsuyu. First, Katsuyu divides her body into many smaller clones, and then attaches herself to a person. Then Tsunade channels her medical chakra through Katsuyu, who then transfers it to the wounded person, healing any damage. To do so, Tsunade must stay inside a ritual seal. This technique apparently requires great concentration and consumes a lot of chakra, but allows Tsunade to heal an enormous number of people at the same time even if she's very far from them. If she runs out of normal chakra, she can use her reserves.

Trivia

 * It should be noted that Tsunade was also able to use this technique while not within the ritual seal. She did this in a final attempt to protect all the villagers just before Pain used Shinra Tensei to destroy Konohagakure.