Place it right after the fib is shown on screen, then follow it with Nope for the denial and FBI Open Up for the mock arrest, keeping the accusation as the centre of the joke before the reaction shot lands.
About this sound
This seven-second clip strings together Kokichi's playful voice lines chanting 'liar, liar, pants on fire' in a bright, teasing tone, with a sing-song delivery that leans into his mischievous personality. It feels cheeky, smug and deliberately annoying, like a classmate calling out a fib just to watch the reaction unfold.