Children getting whisked away by a handsome protagonist and his magical sidekick to fight against "cool things" like pirates and mermaids in a world unlike our own?
Its an Isekai.
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Isekai is this modern trend in anime (and US movies sometimes!! Like Ready Player One), where characters are sent to another world. Sometimes due to death explicitly ("Reincarnated in a New World" plotline: like "I'm a Spider So What"), sometimes just "temporarily" transported (Sword Art Online / Ready Player One, they are "just" playing a video game).
From an "Isekai" perspective: people want two things.
1. A world very different from our own. Completely different "physics" or rules. So magic systems, history, culture, etc. etc. that's nothing like our world. Neverland easily qualifies.
2. A character who explores the new world from our perspective. The main character is always someone "like the audience", who can be ignorant about the new world. (The various characters the protagonist meets are therefore given an opportunity to explain the world to the newcomer, allowing the audience to learn about the world in a natural manner). In Peter Pan, Wendy is the Isekai protagonist.
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Alice in Wonderland, Connecticut Yankee in King Arthur's Court, Wizard of Oz, A Lion, A Witch, and the Wardrobe. The concept happens again and again as a pattern, because its a good framing device. I'm not sure if Peter Pan can be seen as an allegory of death necessarily, any more than "I'm a Spider, so What?" (2021 Anime) could be.
The children are... children... because the main character often should match the profile of the target audience. Not always, but its a good rule of thumb to keep. Children stories will therefore have child-protagonists more often than not (Polar Express, Lion Witch Wardrobe, Harry Potter). There are exceptions (Peanuts has child protagonists but is largely written for an adult audience), but its just the rule of thumb authors seem to use.
The Spider Anime adaption is sadly so badly realised. I recommend to look for the WebNovel (there is an english translation epub out there as a good starting point) or the light novel.
The main character thinks a bunch and speaks little, so anime and manga will miss out. The manga still gets its somewhat good adapted, but the anime is sadly just so bad that it shouldn't be mentioned.
For a good starter isekai anime, "Tensei Shitara Slime datta ken" | "That Time I Got Reincarnated as a Slime!" is a much better anime and gets more points right.
Its an Isekai.
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Isekai is this modern trend in anime (and US movies sometimes!! Like Ready Player One), where characters are sent to another world. Sometimes due to death explicitly ("Reincarnated in a New World" plotline: like "I'm a Spider So What"), sometimes just "temporarily" transported (Sword Art Online / Ready Player One, they are "just" playing a video game).
From an "Isekai" perspective: people want two things.
1. A world very different from our own. Completely different "physics" or rules. So magic systems, history, culture, etc. etc. that's nothing like our world. Neverland easily qualifies.
2. A character who explores the new world from our perspective. The main character is always someone "like the audience", who can be ignorant about the new world. (The various characters the protagonist meets are therefore given an opportunity to explain the world to the newcomer, allowing the audience to learn about the world in a natural manner). In Peter Pan, Wendy is the Isekai protagonist.
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Alice in Wonderland, Connecticut Yankee in King Arthur's Court, Wizard of Oz, A Lion, A Witch, and the Wardrobe. The concept happens again and again as a pattern, because its a good framing device. I'm not sure if Peter Pan can be seen as an allegory of death necessarily, any more than "I'm a Spider, so What?" (2021 Anime) could be.
The children are... children... because the main character often should match the profile of the target audience. Not always, but its a good rule of thumb to keep. Children stories will therefore have child-protagonists more often than not (Polar Express, Lion Witch Wardrobe, Harry Potter). There are exceptions (Peanuts has child protagonists but is largely written for an adult audience), but its just the rule of thumb authors seem to use.