Let’s learn Japanese with manga. What you are going to learn on this page is:
(Please. Do not say to anyone.)
おねがい means ‘please’ when it is used on its own. If you want to make a sentence with please at the start or end of a sentence, you need to use ください for ‘please’.
誰（だれ）means ‘who’. 誰にも means ‘anyone’ which is used in a negative sentence. 言わない（い・わない）is the plain present negative form of 言う which means ‘say’.
Verb ないForm + で means ‘do not + verb’. If you want to say the same thing politely, Verb ないForm + でください is used.