These are the QTE's (Quick Time Events) that pop every once and a while throughout the game. The first one you come across is on CS #23.
The camera will change its angle and the buttons () will pop up on screen. Make sure you hit everyone without making a mistake. They're not all that difficult but if you do miss one by mistake just come back to that Comic Issue later and replay it.
There are a total of 3 QTE's in the game: CS #23, Nonac Issue #286 and CS #00. The achievement will unlock when your score is shown at the end of the last comic.