"I know what your saying" . A way of saying you can relate. Can be used to also say that you know what they means ik same
Friend: " Do you know the feeling when you take 64 selfies just to find that none of them are good."
You: "IKWYS!! That happens to me all the time."
Friend: "Glad I'm not the only one"
ikwypia stands for "i know who you pretend i am." these are lyrics from "Washing Machine Heart" by Mitski. Any cultured person/mitski stan should be able to read this easily.
That girl's status on discord was "ikwypia" shes probably a mitski stan.
I know what you did last Summer is a movie from the late nineties and what happens is four young friend get into a car accident and kill a man they cover it up and then a killer is stalking them.