YOU SAID:

I solemnly swear I'm 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 pledge solemnly.

INTO JAPANESE

私は厳粛に誓います。

BACK INTO ENGLISH

I pledge solemnly.