Let's imagine that you saw your coleague at your office in a very cold morning.
You might say to him or her:
"Hey, it is a very cold morning! You didn't want go out of your house, do you?"
And he or she answers you:
"No, I didn't!"
That means he or she didn't want to go out of your house because it was very cold.

But Japanese (incluging me) often make a mistake to say:
"Yes!"
as the answer to you.

So you might think that he or she DID want to go out of his/her house to go to the office.
But actually, this the answerer wanted to say to you that he/she DIDN'T want to go out of the house.
In this context, this "Yes" means "I agree with you" or "Exactly".

Of course, this is wrong English.
He or she (or I) SHOULD answer "No" to express that the answerer DIDN'T want to go out of the office.
In other words, "I agree with you".

But Japanese often make such mistake.

Let's imagine the other example.
If you were a shopper at the hot dog store and I (Japanese) was a buyer.
You say to me:
"A hot dog, a glass of beer, and a bag of potato. No other request?"

If that was enough, I should say "No" which means "That's all" or "You are right".
But the buyer like me often make a mistake to say "Yes".
It means "I agree with you that I have no other request."
But you misunderstand that I have extra request.

In this situation, in Japanese, we answer "はい (hai)" which means Yes.
This means, I agree with your thought.

In short, if you are using a "negative question", the answerer should say "No" to mean you are right.
But the Japanese often make a mistake to say "Yes" against his/her thought.