In the world of Naruto, many ninjas are capable of summoning animal companions. These summonable animals are often far more intelligent than normal animals and can speak, and many of them assist ninjas in combat or other duties. For example, Kakashi is able to summon a pack of ninja hounds that can help him track targets, while Jiraiya and Orochimaru could summon massive toads and snakes respectively to help them in fights.
Almost any animal summon can have its uses and be a major asset to any ninja. However, one summonable animal stands out from the rest. Both Tsunade and her student Sakura can summon a slug named Katsuyu. At first glance, Katsuyu may seem like any other summon animal that can help out in a fight, but she is much more. Katsuyu possesses a long list of strange and powerful abilities that make her easily the strongest summon.
Katsuyu Can't Be Killed
All summon animals originate from a different world. When a ninja has signed a contract and uses the Summoning Jutsu, they can teleport a creature of their choice to their world. Usually, the more chakra that is used, the more powerful the creature they can summon. The summoned creature is capable of returning to their world whenever they wish, but they can also be killed in the world they were summoned to, as Fukasaku was during the fight with Pain.
However, Katsuyu works differently from other animals. She is a gargantuan slug that's capable of dividing herself into different bodies. When Tsunade and Sakura attempt to summon her, only a small part of her body is teleported to their world. During the Fourth Shinobi War, Tsunade claimed that both her and Sakura working together was only able to summon one-tenth of Katsuyu's entire body. The portion of Katsuyu that they summoned was as large as a mountain range, which means Katsuyu's true size is ridiculously large.
This feature of Katsuyu has a lot of benefits, especially in combat. Because only a portion of Katsuyu is ever teleported, it means that she can never die when summoned. If the summoned portion is destroyed or injured, Tsunade and Sakura can simply summon another portion that's perfectly fine. They don't run the risk of losing their animal companion in a fight like other ninjas do. As long as they have chakra for the jutsu, they always have access to Katsuyu.
Katsuyu is a Capable Fighter
Although Katsuyu lacks fangs, claws or hands to wield weapons, she still manages to be effective in combat. As a slug, Katsuyu can spit a powerful stream of acid. This acid is strong enough to melt through solid rock. In fact, Katsuyu is capable of holding her own against Orochimaru's personal summon Manda, a massive snake.
Katsuyu's ability to divide herself is one of her strongest abilities. Her ability to split herself into smaller copies allows her to avoid attacks like Manda's constriction. This gives her far more durability and evasive skills than most other summons. These smaller copies can also work independently of one another, meaning that they can surround a target or fight multiple opponents at the same time.
Katsuyu is also the perfect summon for information gathering and communication. All the copies of Katsuyu can telepathically communicate with one another no matter the distance. Moreover, Katsuyu can be summoned by multiple summoners at the same time. During Pain's assault of the Leaf Village and the Fourth Shinobi War, Katsuyu played a vital role in sharing important information and keeping everyone informed.
Katsuyu is a Powerful Healer
Katsuyu's full potential is revealed when she is paired with a medical ninja such as Tsunade or Sakura. Katsuyu's copies can attach themselves to an injured person, and she can channel her summoner's chakra to heal them. This gives the summoner a form of remote healing. They can give medical attention to multiple people without exposing themselves to enemy attacks. Tsunade and Sakura were able to heal the entire Allied Shinobi Forces thanks to Katsuyu.
The nature of Katsuyu's body allows her to change the shape and structure of her form. This ability allows her to encapsulate individuals within her body, protecting the individual from further harm. Tsunade used this ability to save the lives of multiple villagers when Pain wiped out the village. Katsuyu is therefore the best support summon, especially when she combines her powers with a healer.
Many of Katsuyu's abilities are unique and bizarre. These abilities often disturb many of the characters around her, but they have saved many lives too. Katsuyu may not have the same level of destructive power as many of the other summons, but her utility more than makes up for it. When it comes to summon animals, the great slug Katsuyu ranks far above the rest.
