Japanese phrase
秘密にします。 hi mitsu ni shi ma su
Meaning
I'll keep it a secret.
When to use it
Promises not to reveal confidential information. It is a polite, reassuring reply when someone asks for secrecy, though it can sound firm when stated alone.
Example dialogue
これ、誰にも言わないでね。 ko re dare ni mo i wa na i de ne
Please do not tell anyone about this.
秘密にします。 hi mitsu ni shi ma su
I'll keep it a secret.