What do ky and c party mean?

The c circle is the role-playing circle of cosplay.

A group of COSER play COS together and form a circle, just like your circle of friends.

The specific meaning of "ky": The surface meaning of this word is that you can't read the air. The deeper meaning is that when everyone is doing the same thing or discussing something, someone does something very strange and out of place, makes a speech, etc., and ruins the atmosphere without seeing anyone. For example, when a group of people are discussing which perfume smells good, if someone says that the leeks they ate for lunch are good, others will say that they are KY.