noun
one's heart of hearts; the depths of one's mind
Literary and somewhat poetic; refers to the innermost thoughts or feelings, often used in introspective or emotional contexts.
彼の言葉が胸奥に響いた。
His words resonated deep within me.
胸奥に秘めた思いを打ち明ける。
I confess the feelings I've kept deep in my heart.