heartstrings; innermost soul
A poetic expression for the deepest, most sensitive part of one's heart or emotions. Often used in the phrase 心の琴線に触れる (to touch one's heartstrings).
His performance touched my heartstrings.
The final scene of the movie stirred the audience's innermost souls.
From 心 (heart) + の (possessive particle) + 琴線 (strings of a koto). The image is of the strings of a Japanese harp that resonate with emotion.