Put it last in the sequence, after the main farewell line, then follow it with a gentle closing sting and a short end card so the video finishes cleanly instead of stopping abruptly.
關於此聲音
This is a very short clip of a single spoken word, bye, lasting under a second. It feels light and final, like a quick wave at the door, and works as a neat sign-off for a friend leaving without drawing the moment out.