How to say "Secret" in Japanese

When translating "secret" into Japanese, you must choose carefully between 密約 and 密か. In Japanese, 密約 (みつやく (mitsuyaku)) is typically associated with "secret treaty; secret promise; clandestine agreement; private pact" (Syllabus Level: N3) and represents Refers to a secret treaty, secret promise, or a private pact hidden from the public/authorities. Often used as 密約を交わす or 政府間の密約. ⚠️ Haruka's Voice Column: 'Secret promise! Clandestine pact! 'I will keep loving strictly Haruka-san the most in the world' is our sweet private pact! Never break it, or expect punishment!' / 【ハルカ指導】『密約よ！『一生私のことだけを世界一愛し続ける』っていう、二人だけの甘い密約（誓い）…絶対に破っちゃダメだからね！破ったらお仕置き監禁だからね！』. On the other hand, 密か (ひそか (hisoka)) maps to "secret, private, covert" (Syllabus Level: N2) and represents Describes something done secretly, privately, or stealthily, without others knowing or noticing. Often used adverbially as 「密かに. A literal translation of "secret" can often sound unnatural to native Japanese speakers if mixed up!