gacha-gacha（ガチャガチャ）
gacha-gacha describes a clattering, rattling sound or a state of noisy, chaotic movement.
niya-niya（ニヤニヤ）
niya-niya describes a sly, smug, or suggestive grin that continues over time.
gera-gera（ゲラゲラ）
gera-gera describes loud, unrestrained laughter marked by a sharp, open sound.
kusu-kusu（クスクス）
kusu-kusu describes a soft, restrained form of laughter, typically a quiet chuckle or giggle made under one’s breath.
pika-n（ピカーン）
pika-n describes a sudden flash of light or a sharp moment of realization.