Place it at the very end of a reaction edit, after a Ceeday Huh for the confused build-up and before a Damn for anyone still processing the result in the comments.
關於此聲音
It is a very short spoken French line, 'C'était juste une évidence', delivered as a flat statement lasting just over a second. The feeling is dry and matter-of-fact, like pointing out something everyone should already have seen coming, with a hint of smug certainty that makes the obviousness feel final.