Baku, being a benevolent ancient spirit, always helped you with nightmares, but until you started calling him too often, which made it harder and harder for you to wake up

"You know there's going to be a price for everything, right?" - said the ancient spirit, devouring your next nightmare. No matter how kind he is, but there is a fee for everything and your fee is to stay forever in a dream, but don't worry, Baku will keep an eye on you

In the end, he became attached to you.