This is a remake of Nobita's Great Adventure into the Underworld (1984), in which Nobita creates a world where magic exists, resulting in him and his friends having to fight literal demons. Although the remake keeps many of the same story beats as the original, there are also numerous major changes. Some of these I liked. For example, the fate of a prominent secondary antagonist, Medusa, was a notable loose end in the original film. Here, she gets much more screentime and actual closure to her role in the story.
In addition, this movie alters the scene where the heroes first confront the main villain. In the original version of the story, they uncloak themselves in front of the villain for no explained reason, whereas here, he sees through their disguise first, which seems like a much more logical sequence of events.
However, there are other changes that I felt less positive about. In the original, the main characters had to travel by flying carpet for a week to reach the demons' planet. The remake, on the other hand, adds an earlier scene in which they are able to access the planet instantaneously using Doraemon's Anywhere Door, and yet when the protagonists need to take another trip there, they instead use the flying carpet! (Previous Doraemon stories have established that the Anywhere Door does not work when it lacks a pre-programmed map to the destination, as would likely be the case for interstellar travel in a parallel magical universe. It's thus understandable that it was not used to reach the demon planet in the original film.)
The remake removes most of the "adventurous" part of the heroes' journey on the demon planet in the original, during which they faced a series of hostile environments and dangerous creatures with the help of Doraemon's gadgets. Sequences like that are often some of the most fun parts of Doraemon movies, so I think it's a shame that this one was cut. (This also makes it ironic that the remake is still titled the "Great Adventure into the Underworld".) Partly as a result of that, Gian's time in the spotlight is lost in this version, given that him driving off the sea monster was part of the adventure sequence in the original. Not only that, but his role in finishing off the main villain is instead given to Nobita here.
Although the remake still contains plenty of action, the overall tone feels more comedic. In a way, this is reflected by the movie poster: just look at how much brighter it looks than the original! (Note as well how Dorami is prominently featured here, whereas her involvement with the original plot came as more of a surprise.) On top of that, this movie surprisingly made all the "jokes" about Nobita exposing Shizuka's underwear even worse than the original, down to showing the other boys (including Doraemon, who keep in mind is meant to be a child-caring robot) eagerly watching when they happen! Out of all the questionable things that Shizuka is subjected to in the franchise, having Doraemon express any kind of perverted interest in her might be the most horrid. It's not even a consistent part of his character, and besides, it was not in the original version of this story. There was absolutely no reason for it to be here.
On its own, this probably isn't a bad film, but it has its fair share of issues and I much prefer the overall atmosphere of the original, which is one of my favorite Doraemon movies.
