When I just started with Shingu, one oddity I noticed immediately was how it featured no defective characters. Sure, some had issues, but overall they are very different from common characters in contemporary anime. Nobody is neurotic, and it feels like something large is missing.
Another facet of the same thing is that stereotypes, upon the development of which anime creators worked so hard and so long, are practically absent. We can formally classify characters, but it's not who they are. Nayuta is not a tsundere, she is just proud and shy and traumatized; Harumi is not moe.
Someone (maybe a commenter) wrote that kids seemed too mature. I don't think so, they seemed exactly matching their age, except for Shun. That guy is definitely way too sly, but fortunately he is too good-natured in general. I think the unusual normality was mistaken for maturity by these observers.
Aside from being stable, most characters are also exceptionally nice, which is incredibly odd, considering. In Figure 17, for example, we have no less than two actively present assholes: Aoyama (the guy with glasses who courts Hikaru), and Mina (the pretty girl with complex braids). In Shingu, however, there aren't any.
Such characterization contributes to a feel that I rather expected from "The World of Narue". It took me about five episodes to get desensitized to this Hello Kitty world and stop wondering what is wrong with everyone.