Maomao no Hitorigoto

For a chibi short, this is a bit different than some others that I've seen in that it follows the story of the main series quite closely. (Don't watch this without watching the main series.) You can watch it in parallel or watch after the main series as a recap. You could probably classify this as an educational series, as mostly it adds a bit of explanatory context to the plot, such as some properties of herbs or poisons, and some symbolism. If you have watched Kimetsu no Yaiba, this series is very similar to the Taisho secrets segment at the end of some episodes, though the info here is more relevant to real life.