Suu

"Well, it was Suu's fault that you caught a cold... I should apologize as well. But Suu doesn't mind! Because she loves her Master!" - Suu talking by herself for the first and only time.

Suu is a Slime Girl that snuck into Kurusu's house without notice while looking for sources of water. She is the  fourth girl to move in with him, albeit unofficially. Prior to her appearance slimes were still considered fictional creatures and, thanks to Ms. Smith not wanting to bother, are still thought of that way outside of the people she interacts with.

Appearance
As a Slime, Suu's true form is a large mass of a transparent blue gelatinous slime. She also has a mass of green "hair" with three yellow "antenna" on the tips. She can shape herself into a somewhat humanoid form that, according to Miia and Cera, is very rare for a slime to be able to do.

Suu normally shapes herself to be about the same the size and build as Papi, but when she absorbs a certain amount of water, she chooses a more mature form: she becomes taller, bouncier, and curvier than usual. The excess water goes straight to her bust and hips. When dehydrated enough, she becomes small enough to fit into a small bucket -- showing as only a head and hands peeping over the rim.

While usually naked, Suu occasionaly wears only a raincoat and boots, since any other clothes would just get wet and dirty from contact with her.

Personality
Suu's method of learning is through mimicking the actions of others; such as Miia, Cera, and at times, Papi. She can be somewhat absent-minded at times; such not knowing that she almost drowned Kurusu and Miia by hugging them, and accidentally adsorbing many objects around the house. She also seems to be very child-like, as shown when she was playing video games with Papi.

However, it's implied that Suu may be not as simple minded and childish as she pretends to be, as seen when she cured Kimihito of his illness by herself and talked without mimicking and when she ruined the directors plans by reading his thoughts and revealing them to everybody.

Suu appeared quite impressed by the protective concern Papi has shown towards her, and seems to have consciously chosen her friend as a role model.

Skills and Traits

 * Invulnerability: Since Suu is made entirely of a liquid-like substance, she is seemingly immune to any form of physical damage, as seen when Centorea's sword just harmlessly passed through her. Even when she solidifies herself, she is still immune to any form of blunt impact, as seen when she used herself as a living shield to protect a girl from being hit by a car.
 * Poison and disease immunity: Due to her unique biology, Suu cannot catch any Human diseases. She is also capable of consuming any foods that could result in food poisoning to both Humans and Extraspecies, without them having any effect on her.


 * Adhesive body: Suu also has the ability to stick to any surface, such as ceilings.


 * Water absorption: As it's seemingly her only basic need, Suu is capable of absorbing water into her body. All she has to do is make physical contact with water and it will be absorbed. However, it's not clear if it happens automatically or if Suu can control it. Depending on how much water she absorbs she can also change her size and body proportions. She can also expel her internal water in pressurised streams from any part of her body. Suu is also capable of filtering her own internal water. It's possible there might be more to it than that, as her filtered water was able to cure Kimihito of his disease.


 * Shapeshifting: Suu seems to have an almost complete control over her own biology, which grants her shapeshifting powers that might even surpass that of a Döppelganger like Dopple. For one, Suu can mimic the appearance of anyone, Human and Extraspecies alike. Suu's shapeshifting is so versatile, she can even transform into clothes or objects, like boxes. She seems to have enough control over her own anatomy that she can control her own solidity and texure, as seen when she transformed into clothes without making whoever wore her wet. Miia once thought of using this ability to have Suu be "worn" by Papi and Mero to disguise them as Humans. The disguises were capable of fooling Kimihito and Ms Smith. However, unlike Döppelgangers, Suu's shapeshifting has one major drawback: her antenna and signature eyes will always be visible. Also, repeatedly changing forms in a short time is exhausting for her.


 * Voice-Mimicry: Suu is also capable of perfectly mimicking people's voices, though she hasn't used it in combination with a disguise yet.


 * Mind reading: When touching someone's head with her antenna, Suu can view their memories, thoughts and emotions.


 * Fast learner: Suu also seems to be a fast learner, having learned to talk interact with others in few days, and later on is able to mimic her friend's word-for-word in order to help them "talk" with Kimihito while he was sick, and eventually started speaking on her own.


 * Eidetic memory: It's implied Suu may possess eidetic memory, as she was capable of perfectly memorizing and mimicking everything that was said and demonstrated to her when Kimihito was sick.


 * Weaknessess: Despite all these strengths, Suu is not invincible. Throwing her in a body of water can temporarily immoblize and stun her, as she becomes diluted. If the body of water is large enough, like a lake, the dilution effect would be strong enough to kill her. Heavy rain is also dangerous to her, as the impact of all the water drops dissolves any part of her body exposed to it. Also, exposing her to higher temperatures dries her out. If she dries out, she shrinks in size, to the point where she can fit in a small bucket, and makes her lose her humanoid form. However, doing so is the equivalent of starving her, and during that time Suu will mercilessly molest anything with even the slightest trace of moisture on them, no matter the circumstances.

Plot
Suu first appeared in a pot while Kurusu was teaching Miia how to cook. The slime latched onto her face and knocked her out before darting into a crack. After Cera tells him what it was, Kurusu goes to wet a cloth for Miia's head; only for the slime to pop out of the small bucket he was using. Cera tried to strike at it with her sword; with no success. Suu then rushed them and left; leaving them both covered in her slime.

The slime later watched Cera and Kurusu as they washed each-other in the shower, and later snuck into the shower. Both Cera and Kurusu panicked, and Cera wound up getting knocked out. The slime then wrapped up Kurusu and revealed a humanoid form; much to his shock. She then began to hug and wash him, mimicking the actions of the other girls while using her body to rinse him.

But then she accidentally absorbed his head into her body, almost drowning him. However Kurusu dove into the water to get her off by diluting her. Later, after she expelled excess water to reform back into her normal form, Kurusu, Miia, and Cera debated on what to do with her while she played video games with Papi in the background.

Trivia

 * She is the only girl not to be brought to Kurusu by Ms. Smith.
 * She is the only character who did not have a name, but rather one was given to her by Papi.
 * Like the other girls however, her name derived from her species name: Suu from Slime. Papi stated this was her reason for naming her so.
 * When Cerea mentions she's disappointed to learn slimes are not as easy to kill as RPGs had led her to believe, she is referencing the Dragon Quest games, where Slimes (the same color as Suu) are usually the very first random enemy encounter and are the easiest monster in the game series to defeat.
 * Suu has a tendency to spontaneously reveal new powers depending on the plot, a reference to the limited knowledge on slimes by the government as they were kept secret by the monster representatives.