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?
That didn't even make that much sense in English.