Carbon

Squiddo with a disease that prevents him from changing his ink to anything but black due to toxins in the ink. He's usually quite arrogant and cocky but breaks down under pressure and becomes very nervous and fidgety. 

His disease also causes him to tire very quickly due to the toxins in his ink and he is therefore pretty lethargic and lazy. Often times he will confidently exclaim he is going to do something then never actually work up the energy to do it.

He and Slosh are a couple and Carbon can be rather clingy with her, getting on her nerves rather often. But they are inseperable regardless.

Streak is his little sister and he is very protective of her, even if she is physically stronger than him due to his illness- they both care about each other a lot even if they talk less than they used to as they've grown older

As with most of my Splatoon characters, Carbon has way more story than this, I'm just...too lazy to write it qwq