Cause he can't figuring out what's going on in the story.
Maybe they're touching each others' backsides.At the same time, I think I mentioned it before, but they look very close, they seem to be hugging each other on the back.
(Readers can use their imagination to fill-in what they can't see. )
Here's the artist insta page: https://www.instagram.com/caturary_cs/