expression, godan verb (-ku)
be frank; speak one's mind; have a heart-to-heart talk
Idiomatic expression meaning to open up emotionally and speak honestly, often in a serious or personal conversation.
See also: 打ち明ける (うちあける)
彼と胸襟を開いて話したら、誤解が解けた。
When I had a heart-to-heart talk with him, the misunderstanding was cleared up.
Why don't you try opening up to your boss and talking it over?