These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Family-Unfriendly Aesop: Episode 4: If something is troubling you, get drunk to forget about it!(Mizuki ends up getting a runner's high instead.)
Nightmare Fuel: In general, Mokkeseems like a straight example of a children's show, so when things become not-so-kid-friendly, the effect is really jarring.
Shizuru's story about a snake being killed, cut into pieces, and impaled by a group of children as a game and then cursing the village leader because he was the one who feared a curse was chilling. Thankfully, it didn't actually happen in the anime.