I wonder if an analysis could be made from all the different characters that have told stories and how they relate to each character personality. Like we know Hina stories aren't as dark as the others for example and are a bit more bittersweet, but what about Yuuma or the policeman ?
Yuuma's stories reflect his current situation and/or mood. I see it as him trying to express his anguish which might just be him being unable to express thing directly, or conversely, because it's required for the ritual, then he might as well express his angst in the form a ghost story.
Both of the policemen told stories that are essentially saying "dude why are you killing us, we're only trying to save you". The first cop's story (Chapter 47) also has hints of telling the audience that Yuuma's case is not as straightforward as it appears (which the cop is implied to have realized after he got cursed), and that the audience should not judge him only by the things we have directly seen. The first cop even talked directly to "us" so it might also represent an attempt at pleading to "us" to leave the boy alone. Most importantly, both cops are presented as genuinely wanting to help because they realize that Yuuma's angst is misplaced - he should have sought their help instead of this occult deal.
As to why Hina's stories seem particularly mellow, it can be down to her having a deep sympathy for Yuuma (I think it's obvious she likes him), and because she knows this is something she herself started. She was the one who suggested the ritual to Yuuma in an attempt to talk him out of outright committing suicide from that window (again see Chapter 1). She was perhaps thinking it will distract him from suicidal thoughts for at least a couple months and he will eventually snap out of it. But then she realizes that Yuuma is actually doubling down on the whole thing precisely because of her suggestion. She feels helpless, not knowing what to do to help him anymore, so she ends up participating in the ritual as well in an attempt to at least stay close to him until the end. Along the way, it is implied that Hina, much like the cops, also slowly realizes that "we" are the culprit. If "we" actually are a photo of Yuuma's real parents, then Hina would surely recognize "us", so it also hurts her knowing that "we" are responsible for Yuuma's obsession in addition to her starting the whole thing in the first place. These conflicting emotions are what give her stories that more tragic, melodramatic tinge.
Looking at Chapter 80 again, I realized that the color page has a ton of hints. It of course has framed pictures of a person whose eyes move to look at the "camera" and even sort of come out of the frame, and the businessmen strolling around have their heads turned 180 degrees just like Possessed Hina. And the caption talks about eyes looking at you from everywhere being the true form of terror. From this and of course the narration in Chapter 1, I think it is safe to say that the key plot point here is that pictures of a (dead?) person can be a gateway to the underworld and whatever is looking at you from inside it is trying to get out.