相あい済すまない

i-adjective

very sorry; remorseful; apologetic; contrite

Formal, somewhat old-fashioned apology. Often used in business or official contexts to express deep regret. The 相 prefix adds a sense of mutual or thorough feeling.

• ご迷めい惑わくをおかけして相あい済すまない気き持もちでいっぱいです。

  I am filled with a feeling of deep regret for causing you trouble.

• 相あい済すまないが、もう少すこし待まってほしい。

  I'm terribly sorry, but I'd like you to wait a little longer.