A placeholder journalists use when they need to find additional info in a headline or story. If you see this on a news website, somebody's made a mistake.
"Tktk" is an offensive and derogatory response used with the intent of the recipient to not recognize it as an insult. Like flicking off an infant, or cheerfully cussing someone out in a language they don't understand.
Guy:"Dude, that jacket totally makes you look like Justin Bieber."
Dude:"Tktk."
Guy:"...?"
Boys who enjoy yaoi (a genre in Japan that contains sexual and/or romantic relations between two men); literally translates to "rotten boy"; corresponding female : fujoshi