Put it right on the scare beat, after a WhatsApp message sound sets the scene, then cut to a Kiko laugh to follow it with laughter and keep the edit moving.
このサウンドについて
This is a very short human gasp, just under a second long, with a single sharp 'A!' cried out in sudden fright. It feels startling and a little comic at once, like catching someone mid-flinch, and it lands best as a tiny jolt rather than a long reaction.