There's not much to say about Kleine. They don't speak, they aren't ever seen eating, they're covered in scars and they have two tentacles coming from their back.
Kleine is a circus performer. Part of an acrobatics act and sideshow. They become very attached to anyone who shows them even the slightest kindness, which may be how ze was originally brought into the troupe. Ze is very shy and tends to avoid people whenever possible. They also have never been seen without their gas mask and clothing of some sort, so their facial features and gender are unknown.
Kleine's tentacles are extremely strong and sensitive. They can cling to a ceiling or wall with them, lift objects that would normally be too heavy, and use them as a second pair of arms. They also, possibly, act as their eyes. Kleine feels around with them constantly, moving them in whatever direction they are walking, or noise is coming from.
Since they either can't or refuse to speak, no one knows Kleine's real name or where they came from. Their name was given to them by one of the circus performers because of their size.