Suu

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 by humans 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. For easier interaction with Humans, Suu shapes herself into a somewhat humanoid form that, according to Miia and Cerea, is unheard of 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 occasionally wears only a raincoat and boots, since any other clothes would just get wet and dirty from contact with her, or wouldn't fit due to her constantly changing sizes.[2]