Istw
Istw means "I swear to Woojin". Kim Woojin is a member of the male k-pop group "Stray Kids". He is considered god since he is just so perfect and there's also a religion called Wooligion created by the precious Stays.
A: I heard that your friend C told everyone your secret.
B: Istw I'm gonna kill him.
B: Istw I'm gonna kill him.