This is so terribly sad, but only if you have seen Made in Abyss - Movie 3; Dawn of the Deep Soul (2020), otherwise it becomes just a silly little piece of childish enthusiasm. This story highlights children's intrinsic innocence and their unconditional love of those who are close to them. Children cannot fathom evil, that is a learned experience, and believe all grown-ups to be as honest as themselves. Therefore they become utterly confused when they are faced with the practical results of evil. There is a lesson here: Are not children, in their innocence, more human than "sophisticated", clever adults? The art is somewhat sketchy, butthat goes with the territory.
The intro is very similar to early 20th century shorts made in the U.S of A. A coincidence? I think not.