I'm not sure where you are since your reading the Manga you could be ahead of me. In the show its going into his mouth because Itachi gave Naruto some of his powers on the chance that Saskue attacks Konaha.
One alternative approach could be for the fox to compliment the crow's singing voice, insisting that the crow should showcase its beautiful voice by opening its mouth to sing. This tactic could potentially appeal to the crow's vanity and prompt it to open its mouth willingly.
In chapter 19 of "The Westing Game," Mr. Hoo gives Crow a luxurious mink coat as a gift. This surprises Crow, as she is not used to receiving such extravagant presents.
badomen
The Fox was trying to get the cheese by flattering the Crow.
In Chinese culture, a person who speaks with a 'crow mouth' says bad things off others.
chapter 19: odd relatives, when j.j. ford is doing her investigation. on page 134(depending on what book you have.) it says she is 57 years old. (p.s. i hate this book with a burning passion, it took me forever to find that answer!!!)
The purpose of the fox in flattering the crow, in Aesop's fable The Fox and the Crow, was to get the crow to drop the piece of cheese that it was carrying in its mouth. The fox flatters the crow by saying that it must have the most lovely singing voice and that the fox would love to hear but one song from the crow. So the crow begins to caw and so drops the cheese which the fox takes.
the crow-girl goes to the shop and buys four pigs because she likes bacon !! and then she farts on a fire and starts a hurricane ... the whole village is wiped out because the bacon made the crow-girl gassy !!
the fox flatters the crow and then asks the crow to sing for him noting that he must have an excellent voice to match his excellence in every thing else. when the crow opens his mouth to craw the food he was holding falls out and the fox catches it and eats it. so simply put the answer to your question is flattery.
There are two similes in the first chapter of "Where the Red Fern Grows." One example is "straight as a crow flies" and the other is "as smooth as glass."
A bird's mouth is an interior angle or notch cut across a piece of timber for the reception of the edge of another - also called a crow's foot in the United States.
If a black crow has its mouth wide open, it could be a sign of various behaviors. Often, it indicates the bird is vocalizing, either calling out to other crows or expressing agitation or excitement. Additionally, crows may open their mouths to regulate their body temperature, similar to panting in other animals. Observing the context and surrounding behavior can provide more insight into what the crow is communicating.