expression, godan verb (-su)
empty vessels make the most noise; the silent firefly burns with more passion than the crying cicada
Proverb contrasting noisy, showy people with quiet, passionate ones. The literal image is of a cicada that cries loudly versus a firefly that burns silently but intensely.
He doesn't talk much, but as the saying goes, the silent firefly burns with more passion than the crying cicada; he harbors a strong passion inside.