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Although it has never been properly described in the manga or the databooks, a sensor-type or sensory-type (感知タイプ, Kanchi-taipu) is a classification used for shinobi that have the ability to feel and locate an enemy or even notice fluctuations in their chakra using their senses. 

Naruto chapters 620, 464, 460 & 334.

The series introduces a handful of ninjas able to detect chakra from the start. It shows that any shinobi has the ability to sense fluctuations in chakra without being a natural sensor-type, especially for foul or powerful signatures.

For example, almost every ninja close to Naruto’s circle has been able to detect his aura when he summons Kurama’s chakra due to being very powerful and dark.

These basic abilities also apply to Sakura as genin, chūnin and jōnin; despite not coming from any clan.

Naruto chapters 616 & 233.

Naruto chapters 28 & 685.

According to the third databook, written by Masashi Kishimoto, sensor-types are useful to track or pursue targets, and they are divided into groups based on the medium used for the sensing. Some of them include smell, like the Inuzuka Clan; eyesight, like the Hyūga Clan; or even using animals or other people, like the Yamanaka Clan with their Mind Body Switch Technique and the beetles of the Aburame Clan. 

There are also other shinobi that use special techniques or that create their own.

Third databook.

Some of them include smell, like the Inuzuka Clan; eyesight, like the Hyūga Clan; or even using animals or other people, like the Yamanaka Clan with their Mind Body Switch Technique and the beetles of the Aburame Clan. 

There are also other shinobi that use special techniques or that create their own.

Naruto chapters 395, 481 & 332.

This way, the term sensor-type or sensory-type ninja is introduced in chapter 355 by Kakashi Hatake and used to describe Hinata Hyūga. She falls in the subcategory of sensors that use their eyesight as a medium to see an enemy or see their chakra, like it is mentioned in the databook. The Byakugan is able to see the enemy in the distance and also see their chakra.

Naruto chapter 355.

The most common kind of sensor-types are those that can sense the chakra given off by a ninja and it is a superior skill among them. Shinobi from the Yamanaka clan, Tobirama Senju, the second Tsuchikage or Karin are examples of this type. Karin, in particular, is currently the most exceptional innate sensor-type in the world.

Naruto chapters 475, 627, 547 & 363.

Being a sensor-type is a very beneficial and useful skill in battle as it allows the user to locate an incoming enemy, anticipate jutsu or identify genjutsu; however, it varies depending on the skill of the user or the medium they use to track signatures. Not every sensor-type is able to do all the things listed above, it requires skill or even the use of powerful sensing techniques to achieve them. 

Karin is an example of a sensor-type that can anticipate an enemy by perceiving their chakra or even identify genjutsu by analyzing her own or her comrades’ chakra. Likewise, Neji Hyūga can anticipate an attack by viewing the concentration of chakra of his enemies. 

Naruto chapters 380, 477 & 193.

Those shinobi that are not naturally sensor-types can use sensing techniques with mediums adapted to their abilities. For example, Naruto Uzumaki is not a natural sensor-type, but Sage Mode grants sensing skills, which are later enhanced with Six Paths chakra and allowing him to sense even invisible enemies withing a very wide range. Kurama also allows him to detect negative emotions.

Naruto is not actually an innate sensor-type, but it is his training in Sage Mode and another being, Kurama, what give him sensing skills.

Naruto chapters 431, 674 & 505.

The same way, sensor-types can boost their abilities using sensing techniques too, the best example being Karin. 

Third databook.

The Mind’s Eye of Kagura is a powerful sensing hiden technique that allows Karin to track signatures located several kilometers in the distance, as well as very specific characteristics like the number of beings, their race, their pace or if they are lying. According to Sasuke, she is the only person in the world with this ability, which makes Karin the best among sensor-types.

Naruto chapters 365 & 457.

The manga proves that sensing is a basic ability within any shinobi’s reach, as long as there is some kind of training or special conditions that facilitate the perception, like large chakra or dark signatures such as Tailed Beasts. Those that can innately sense chakra possess a high-skill among sensor-types, and they’re normally shinobi of clans.

Coming from a civilian background, of course Sakura is not a natural sensor-type. But, has she ever displayed sensory skills? Actually, she has. As aforementioned, it is possible for ninjas to feel large or foul chakra signatures without necessarily being adept at sensing. With the training of a kunoichi, Sakura has displayed those basic sensing skills throughout the manga.

The earliest record of Sakura being able to detect chakra signatures is when she felt Zabuza’s dark chakra and his intention to kill Team 7 during the Land of Waves mission. Zabuza’s sinister aura was so intense that even Tazuna could perceive it, and he is not even a ninja.

Naruto chapter 12.

While this was not pointed out the first time during Naruto’s fight against Neji in the Chūnin Exams, Sakura can feel the immense chakra of a tailed beast, like it is common. This was later shown when Team 7 found Orochimaru and Naruto manifested the power again. 

Naruto chapters 292 & 293.

There is evidence of sensory skills being refined with experience. This happens to be Sakura’s case. After her training with Tsunade and as she grew older, Sakura could sense Sasuke’s change after he fell victim to the Curse of Hatred, just as Karin had noted, as well as the chakra of his Amaterasu.

Naruto chapter 482.

Naruto chapter 484.

The last example of Sakura displaying sensing skills is when Madara’s body was being consumed by Kaguya. Another example of great amounts of chakra powerful enough to be perceived by non-sensors.

Naruto chapter 679.

Of course, being able to sense strong or foul chakra signatures will not make Sakura a natural sensor-type and it is not the same level of technique as an innate sensor. Being able to detect chakra is a superior skill, but it can be refined with training. 

However, using sensory techniques does make a ninja a sensor-type, it is what happens to Naruto with Sage Mode. There are also other ninja that use jutsu for the purpose of sensing. 

Naruto chapter 430.

Sakura actually has two techniques that are applied to sensing, one that she created and one granted by her summon. 

One of the three summons from the “Three Big Unexplored Sage Regions”, Katsuyu, is one of the most powerful summons in the series. Not only does she possess healing properties, but also sensory skills enhanced with her ability to multiply and her connection with the Byakugō no In.

Although Sakura never used Katsuyu’s sensing skills, the moment she could invoke the Strength of a Hundred seal she gained a sensing technique through the slug. Because Katsuyu is linked to the seal and uses its chakra, the master will be in contact with everybody that the slug touches. When Katsuyu touches a person, she is automatically connected to their chakra, and the slug is symbiotically connected with the Strength of a Hundred seal. 

Naruto chapter 427.

Sakura was automatically connected with the Alliance as soon as Katsuyu’s fragments reached every member. 

However, after the Ten Tails used its arms to drain the chakra of members of the Alliance, she could not know about their condition because the beast had also drained the Katsuyu fragments, thus breaking the connection. 

Naruto chapters 634 & 293.

With her first sensing technique secured, Sakura actually refined her skills even more as an adult, when she reached jōnin rank. According to Sakura Hiden, she can try to feel people by concentrating, just like she did when she was looking for Sasuke around the area at the end of the novel. It is important to note that neither Ino, a chakra sensor-type, or Hinata with her Byakugan, could sense Sasuke presence.

Sakura Hiden

The most impressive thing is that not only does she have basic sensory skills, but she has actually created her own sensing technique, that applies only to her, using chakra as a medium. This is a unique feat among sensor-types and it is what would solidify her new classification.

Sakura’s new jutsu debuted in Sasuke Retsuden. It is described as a technique that only Sakura, a complete master of chakra control, can use by channeling her chakra onto the walls to feel things by contact, such as a complete structure, rooms or hidden objects.

Sasuke Retsuden chapter 4 and novel chapter 3.

Sakura’s jutsu is classified as a contact-type (接触タイプ, Sesshoku taipu) sensing technique. These are special sensing techniques to detect objects or people by contact, that is, when a body touches the range of the jutsu. This is confirmed by the second Tsuchikage, Mū.

Contact-type are considered unique among sensing techniques. 

Naruto chapter 524.

Sakura’s jutsu is not the only contact-type sensing technique used in the series. There are three characters that use a similar method as Sakura, except using a different medium than her: Gaara and Kidōmaru. 

Tobirama Senju and Minato Namikaze also use a method that includes touching the ground to perceive enemies within an area, much similar to Sakura’s jutsu.

— Concealed Sand Picture Cat is a contact-type sensing technique used by Gaara that perceives objects by touch perception, just like Sakura’s own jutsu. He uses his sand as a medium, which is infused with this chakra, and is able to sense the second Tsuchikage in his undetectable form.

Fourth databook.

Naruto chapter 524.

— Spider Web Area works the same way as Sakura and Gaara’s sensing technique. Kidōmaru uses spiderwebs thinner than hair that are infused with his chakra. He is able to sense an enemy when they touch the sensitive spiderwebs.

Second databook.

Naruto chapter 186.

— Tobirama and Minato use a “technique” that is the closest approach to Sakura’s. By touching the ground with their fingers, they could detect enemies in the surrounding area. 

Naruto chapter 481.

Naruto chapter 239.

However, it is unknown if they use chakra as a medium, since it is described that scattering chakra for that purpose is a feat unique to Sakura due to her incomparable control of chakra. It is also to be noted that both Kage, especially Tobirama, are adept chakra sensor-types. In Minato’s case, he had already sensed his enemy before he proceeded to use this “technique” to countt he number of them.

Naruto chapter 239.

The difference between Gaara, Kidōmaru, Minato, Tobirama and Sakura is that she is the only shinobi that uses a contact-type sensory jutsu that can detect inanimate objects. These include hidden traps and mapping structures such as buildings. This is a feat that only her, and one shinobi clan, can use, and it makes her a unique sensor.

Sasuke Retsuden novel chapter 3.

Among sensor-types, Sakura’s technique is very similar to the abilities of a Byakugan, a dōjutsu of sensory shinobi from the Hyūga Clan that can also see through some obstacles and detect objects. The Hyūga use a Kekkei Genkai and Sakura uses a created jutsu based on chakra control.

Naruto chapter 186.

Boruto: Naruto Next Generations episodes 152 & 138.

Still, Sakura has only ever been shown sensing objects or traps but never people. However, it is highly likely that she would be able to sense people using the same method. If Sakura can perceive objects that do not emit chakra, she should be able to detect people that give off an aura.

With basic sensory skills and two sensing techniques that allow her to map structures and feel chakra with Katsuyu, Sakura is the only sensor-type alive, that is not from the Hyūga Clan, that has a unique sensory technique only applicable to her. This is a feat among sensors.

This way, Sakura would fit into three shinobi classifications: medic-ninja, being the best in Konoha; genjutsu-type, the only confirmed in the series; and sensor-type given her techniques.