Kerokko Demetan

Kerokko Demetan, also known as Adventures on Rainbow Pond, is a family-friendly anime that tackles mature themes in a dark and unexpected way. Despite being rated G, it is one of the darkest anime I have ever seen.

— PLOT —
The story follows Demetan, a young frog who survives a genocide on tree frogs from a group of salamanders. After being separated from his family, he finds himself lost in a foreign land. A female frog named Rantan saves his life and helps him reunite with his father and mother. Demetan quickly falls in love with Rantan, but little does he know, she happens to be ... the daughter of the cruel ruler of the pond in which he will be living.

— EPISODIC —
The anime has a strong start in the first two episodes, but the rest of the series becomes episodic, which is both the show's core strength and weakness. Many of these episodes fail to focus on the main cast, with only one or two new characters appearing for a single episode. Some of these episodes explore mature themes related to the main theme of the story, which is that 'the world can be cruel'. Parenthood, slavery, deception, capitalism, forgiveness, friendship, rebellion, racism, religion, and other themes are explored or at least were showcased.

— INCONSISTENT CHARACTERS —
There are some inconsistencies with the main characters, particularly Rantan, which may be due to the fact that the episodes are written by a variety of writers. For example, Rantan is suddenly hostile to Demetan after a conflict was resolved in the previous episode.

— THE BRAVE FROG —
The anime has an English dub which was aired in a movie format called 'The Brave Frog', in which the English studio combined the first two episodes and two other random episodes from the series. While I was initially interested to see how the series would wrap up, I ultimately found the ending to be underwhelming. Personally, I believe the real charm of the show lies in its episodic structure. In fact, I found myself enjoying these stand-alone episodes more than the overarching storyline. Thus, I do not recommend watching the dubbed version, which was basically a rushed summary of the original series.

— VERDICT —
Kerokko Demetan is a unique and interesting anime that tackles mature themes in a family-friendly way. While the episodic nature of the show may be off-putting to some viewers, the exploration of mature themes is worth watching. However, the inconsistencies in the main characters may be frustrating to some viewers. Overall, I recommend giving this anime a chance, especially if you are interested in mature themes in a family-friendly anime.

Two more anime classics from the 1970s that were targeted to children but were quite dark:
* Chirin no Suzu (1978) * Gamba no Bouken (1975)