noun
loyal heart; devotion; fidelity
Refers to a sincere, faithful heart or spirit of loyalty, often in a somewhat literary or formal context. More abstract than 忠誠 (loyalty as a principle).
彼の忠心は誰もが認めるところだ。
Everyone acknowledges his loyal heart.
忠心を尽くして仕える。
Serve with utmost devotion.