If the arrest was in US, bad news. but still can remedy

Since the arrest was in Japan, you might not even get picked as the record may not your arrest in it. (this is not suggest people to lie about their past arrest). See your luck if you chose not to clarify the matter with USCIS.
any arrest, you must have the final disposition (court documents proving the judgment on your case).

You can still apply for a waiver if the crime is not related to moral turpitude such as (family violence, felony, and misdemeanor for imprisonment for over 1 years).

You might be fine. It's not the end