When a cough is used to indicate you think the exact opposite of what you just said, often the cough can be used to disguise saying what you actually think.
1. Yes, I'm sure you don't fancy him (sarcastic coughing fit)
2. Yes, he made the first move *cough* you so came onto him *cough*
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