YOU SAID:

I solemnly swear I am up to no good

INTO JAPANESE

私はよからぬを誓います

BACK INTO ENGLISH

I solemnly swear

INTO JAPANESE

私は厳粛に誓います

BACK INTO ENGLISH

I do solemnly swear

INTO JAPANESE

私は厳粛に誓うか

BACK INTO ENGLISH

I solemnly swear?

INTO JAPANESE

私は厳粛に誓う?

BACK INTO ENGLISH

I solemnly swear?