Nega-Suu

Nega-Suu is a giant Black Slime that stowed away aboard a cargo container ship to Japan. Upon discovery, the President of the Black Lily Advanced Materials Laboratory attempted to transport her to his facilities without the government's notice but a chance encounter with Suu saw Nega-Suu escape her transport truck and enter the water canals around Tokyo. An aggressive and stronger slime, Nega-Suu found Suu's unique experiences desirable and intended to draw Suu to her and absorb the smaller slime's body into her own; eating the smaller Slime's core to gain her experiences and abilities.

Appearance
As a Black Slime, Nega-Suu's body can take different forms depending on how much water she has ingested. She is black in color due to the impurities in her body.

In her blob form, Nega-Suu resembles a giant octopus-like mass, with the ends of her tentacles having pointed appendages. Similar to Suu, she has a long Slime tentacle on top of her head. As Mr President explains in Chapter 54, Nega-Suu's body has taken on a gel-like consistency from her constant water intake, making her no longer soluble in water.

After Nega-Suu accidentally absorbed a small part of Suu's body in Chapter 52 and the polymer that the Black Lilies staff used against her drained too much water from her, Nega Suu's body took on a more solid, humanoid form. In this form, Nega-Suu mostly resembles Super Suu, but with a more aggressive appearance. She has sharp fingernails on her hands, and spike-like appendages on her shoulders, the ends of her tentacles, on her elbows, and on her knees.

Personality
Not much is known about Nega-Suu's personality, or if she is even fully sentient. What is known is that she is a highly aggressive predatory Slime, who is extremely determined to absorb Suu to add to her own capabilities. Due to this aggressive and determined nature, Nega-Suu does not seem to care about the repercussions of the damage she does, even if that includes the deaths of others. Thus Nega-Suu can easily be regarded as one of the most dangerous Liminals that Kimihito and his houseguests have encountered so far.

While it's not entirely clear whether Nega-Suu is fully sentient, she was at least able to act out a plan as shown in Chapter 52 when she communicated with Suu to lure the intelligent Slime girl to her. She also addressed Suu by her name, which implies that Nega-Suu has at least a basic understanding of self-awareness.

Despite her malevolence, Nega-Suu also seemed to develop a softer side of her personality later on, because in Chapter 66 it can see how she read a book in the captivity of the Black Lily Laboratory, which shows an open interest in this activity. It can be assumed that the main reason for this activity is to allow Nega-Suu to gain experience on its own, which makes it unnecessary to absorb an intelligence Slime. Later, Nega-Suu created dozens of new humanoids Slimes, although the reasons for this creative, perhaps even maternal act are completely unknown.

Since Black Slimes are created when the home of normal Slimes are polluted with toxic waste, it can be assumed that Nega-Suu originally had another personality, as Suu is also known that certain substances such as poisonous plants can change your personality for a short time.

Physical Traits

 * Liquid Body: As her physical makeup is a liquid substance, her body acts in the same way. She can place people and objects inside of her body, or have them pass through. This makes her difficult to catch, as she can simply pass through the restraint, such as with Rachne's webs.
 * Invulnerability: Her physical makeup also makes her seemingly immune to any form of physical damage. Even when she solidifies herself, she is still immune to any form of blunt impact.
 * Adhesive body: Nega-Suu also has the ability to stick to any surface, such as ceilings.
 * Acidic body: The acidic properties of Nega-Suu's body are far stronger than those of regular Slimes. This is due to her evolving to break down nutrients in even the most inhospitable of environments.
 * Water absorption: Nega-Suu is capable of absorbing water into her body. For some reason, she is able to absorb far more water than any regular Slime as she can grow to giant sizes purely by absorbing water. She can also expel her internal water in highly pressurized streams from her mouth.
 * Assimilation: Nega-Suu is able to absorb other Slimes into her body, fully assimilating the other Slime's knowledge, memories, and experiences, and fully removing any trace of that Slime's individuality. Assimilating a small part of Suu's being allowed Nega-Suu to take on a humanoid form similar to her.
 * Dilution immunity: As opposed to other slimes, Nega-Suu is somehow able to prevent herself from dissolving when exposed to large bodies of water, such as lakes or rivers. This is due to the large amount of contaminants she has absorbed.
 * Skeletal Structure: Highly unusual for a Slime, Nega-Suu has formed her own endoskeleton to support her body. This skeleton is made out of the impurities stored in her body for a long time.
 * Duplication: As shown in Chapter 66, Nega-Suu can reproduce by absorbing filtered onsen water containing the DNA of Liminals that have bathed in the water. In doing so, she created the Hot Spring Slimes, who also have individual characteristics of other Liminals, such as Nekomimi ears, due to the Liminal-DNA with which they were created.
 * Weaknesses: Despite lacking a Slime's biggest weakness, Nega-Suu can still be defeated. For one, the proper chemical substances can rid her of most of her internal water. Likewise, like all Slimes, Black Suu is completely powerless should her core be removed from her body and isolated from any liquids.

History
Not much is known about Nega-Suu's past, but according to the Slime info card, a Black Slime evolves from a normal Slime when its home is polluted with toxic waste. It is possible that this event led to Nega-Suu's aggressive nature in the first place, although this is unconfirmed. According to Nega-Suu's secrets, up until the events of Volume 13, she didn't have much to do with humans, which made her not much educated or experienced.

At some point, Nega-Suu stowed away on a freighter owned by Black Lily Advanced Materials Laboratory, in an attempt to enter Japan for reasons unknown. The crew of the ship found her in one of the containers, and managed to capture her inside a tanker for transport. Although no one could explain how Nega-Suu got on the ship in the first place, Mr President saw this as a good opportunity to study the Black Slime, so he hurriedly obtained import papers for her. However, since the normal procedure for this would have cost too much time and money, Mr President filed for an exception under "new materials for EXPO use".

Mr President later suspected that the reason why Nega-Suu wanted to come to Japan was to absorbed Suu to gain all of her experience. However, if Mr President's assumption is correct, it remains unclear how Nega-Suu outside of Japan could have even found out about Suu's existence.

Zoological Classification


Black Slimes (スライム, Burakku Suraimu) are slimes that have turned black because their homes are polluted by toxic waste. It is impossible to determine their original color. Though they often make dark and satirical comments on society, they are not careful with their word choices and don't generally understand what they are saying. They are extremely violent and hostile to humans.

Trivia

 * Nega-Suu can be considered one of the most vicious characters in the manga-series, as she is also one of the few one who willfully and almost successfully tries to kill a main character.
 * In Chapter 54, Mr President states that his company has implanted a transmitter on Nega-Suu so that she can be located at any time. However, it is unclear how it should even possible to implant a transmitter into a slime, since a slime is liquid, which is why a transmitter cannot be attached anywhere. In addition, there is the fact that Nega-Suu is a black slime, so a transmitter would be decomposed by the acidity of Nega-Suu's body.
 * Mr President suspected in Chapter 54, that Nega-Suu only wanted to come to Japan to absorb Suu. However, this assumption also raised the question of where Nega-Suu found out about Suu's existence at all.
 * Unlike Suu, Nega-Suu has no pupils even in her humanoid form. This is probably a deliberate stylistic device by Okayado to show Nega-Suu's violent and possibly not fully sentient nature.
 * In Chapter 81, a Slime girl appears who bears a strong physical appearance to Nega-Suu, which is further supported by the fact that the Black Lily Laboratory uses the Slime girl to filter the water in the Black Lily Waterpark, similar to how they also used Nega-Suu in Chapter 66 to also filter the onsen water in the Arctic Inn. However, in Chapter 81 it is not confirmed beyond doubt whether the filtration Slime girl is really Nega-Suu, as neither Kimihito nor someone else identify the girl as Nega-Suu.
 * Since the filtration Slime girl is also a "daughter" of Suu's mother, this would mean that Nega-Suu, if she is really the filtration Slime girl, almost killed her own sister by attempting to absorb Suu in Volume 13.