expression
good fences make good neighbors; a hedge between keeps friendship green
Proverb meaning that even close friends should maintain appropriate boundaries to preserve the relationship.
親友だからといって何でも話すのは考えものだ。近しき仲にも垣を結えというだろう。
Just because you're close friends doesn't mean you should share everything. As they say, good fences make good neighbors.
A traditional Japanese proverb. The exact origin is uncertain, but it reflects a common cultural value of maintaining respectful distance even in close relationships.