Board Thread:Theories and Rumors/@comment-36062903-20180917225941/@comment-36136788-20180920035612

Yang represents female and Yin represents male. But the Yin and Yang symbol has many other meanings too, opposites always, to resemble balance between the two sides.

I think when Jay practiced asking Nya to be her Yang means he is asking her to be more than just a girlfriend since they already are in that girlfriend + boyfriend relationship plus the so very many other reasons we can come up with to support that.