noun
one's real intention; true heart
Refers to a person's sincere, unfeigned inner thoughts or motives, often contrasted with outward words or appearances.
彼の言葉よりも、実の心を見抜くことが大切だ。
It's more important to see through to his real intention than to take his words at face value.
彼女は笑顔の裏に、実の心を隠しているように見えた。
Behind her smile, she seemed to be hiding her true feelings.
本心 is a more common and general term for 'true feelings' or 'real intention'. 実の心 is a less frequent, more literary or emphatic expression.
真意 focuses on the real meaning or intent behind words or actions, while 実の心 emphasizes the sincere inner heart.
Compound of 実 (まこと, 'truth, sincerity') + の (possessive particle) + 心 (こころ, 'heart, mind'). The exact historical derivation is uncertain, but the phrase is used to express one's genuine inner thoughts.