Harin

Inside the giants like Harin in this world, there is acidic gastric juice that does not dissolve the little people, so the little people often play inside the giants' stomachs.
Occasionally, the giants do not recognize the little people, and the acidity of the gastric acid becomes stronger, so the little people can dissolve, so there is a separate space in the giant's stomach where the gastric acid does not reach for the little people.
And the little people often play using the giant's esophagus as a slide.