Someone or something that goes along with something else is accompanying. You might send an email with an accompanying photograph of your new puppy, for example.
Accompanying is related to company or companion. So think of the word as being about keeping someone or something else company, of being its companion or its friend. If you are accompanying, then the main focus is not on you. A report on animal abuse may give us all the grim facts we need to know, but the accompanying pictures bring it all home.