expression
there's no smoke without fire
Proverb meaning that rumors or suspicions usually have some basis in fact.
彼が急に辞めたのは、火のない所に煙は立たぬで、何かあったに違いない。
He suddenly quit; where there's smoke, there's fire—something must have happened.
A Japanese proverb equivalent to the English 'there's no smoke without fire.' The exact origin is uncertain, but it is a natural metaphor found in many cultures.