expression, godan verb (-su)
speak frankly; have a heart-to-heart talk; open up to each other
Idiomatic expression meaning to speak openly and honestly, often in a serious or personal conversation where both sides reveal their true feelings.
今夜は腹を割って話そう。
Let's have a heart-to-heart talk tonight.
彼と腹を割って話したら
When I spoke frankly with him, the misunderstanding was cleared up.