good fences make good neighbors; a hedge between keeps friendship green
Proverb advising that even close friends should maintain some boundaries or formality to preserve the relationship. Similar to 親しき中にも礼儀あり.
See also: 親しき仲にも礼儀あり
As the proverb goes, 'good fences make good neighbors'; even with close friends, manners are important.
A Japanese proverb of uncertain origin, likely adapted from a similar Western saying. The expression uses classical grammar (親しき as the attributive form of 親し) and the metaphor of a fence (垣) to convey the importance of boundaries.