Its just like a smol pet from Ari. Kywa also means smollest garden gnome cuz she a dummy and a smol cät.
''Hey Kywa u are a smol ass!''
Baia Baia means that Yuki does not think what your doing is okay. You will probably suffer from a Painful death in ages days after she says those words or maybe you will live but only if she likes you.
Person A: Yuki is Ugly.
Yuki: Du Baia Baia!
Person A dies a few Days after Yuki saying this.