My answer was not accurate enough. I'm not sure if the anime has been adapted, but it's not true that Rem survived. In " Rem: Life in an alternate world from scratch," the female protagonist Rem was sacrificed in the fourth volume of the novel instead of surviving in the anime. My answer may be wrong. Thank you for your correction.
Life in the Other World from Zero was an animation, not a novel. I'm not sure which part I'm referring to when I say that Rem fell asleep in the last episode. However, in most cases, the characters in the animation would usually fall asleep at the end of the story to rest and recover their energy in the following scenes. If you want to know more about the plot of re's life in another world from scratch, it is recommended to watch the original work or other related resources to get more accurate information.
In terms of the overall ninja world, Kushina's survival could have a ripple effect. Her presence could have deterred some of the villains or influenced their actions differently. For example, Orochimaru might think twice about attacking Konoha if Kushina was there to defend it. And the Akatsuki might have to reevaluate their plans since Kushina's skills in sealing jutsu could pose a significant threat to their goals.
I don't know what 'Rem book' means. Can you provide more context or information? I will try my best to answer your questions.
In "RE: Life in the Other World from Zero", Rem had many endings. In one of the lines, 486 did not have the ability to return to death. He eloped with Rem and formed an ordinary family. They had a son and a daughter, and Rem accompanied 486 for the rest of his life. In the main storyline, after the battle against White Whale, Rem and Crusius returned to the capital to recuperate. They were attacked by Gluttony midway, and Rem's name and existence were swallowed. After that, she fell into a coma. In the sixth chapter of the Web novel, Rem woke up but lost her memory. She didn't remember anyone like Pleiades Ayatsuki. This ending sparked a lot of discussion among the readers. Some people were worried that she would be "eliminated", while others thought that this was her chance to be reborn. In the final plot of the 90th chapter [Corridor of Memories], Pleiades Ayatsuki and Rem (and her satiated sister) were sent to a strange place alone. The original author seemed to want everyone to wait and see what would happen next. In addition, in the ending of Rem's manga, Rem realized her dream and started a family with Pleiades.
The main differences are in the visual style and some character expressions. The manga might have more detailed panels, while the anime could focus on dynamic animations.
Rem is very loyal. Once she decides to trust and support Subaru, she is unwavering in her commitment. For instance, she will fight alongside him without hesitation in dangerous situations.
In the anime " Rem: Life in the Other World from Zero ", Rem did not die but was imprisoned in the prison of the Other World from Zero, so no one else had seen her. Rem was a powerful Magician. She had once lived with Ange and became a powerful Magician with his help. However, Angor betrayed Rem and locked her up in a prison in the foreign world. Since Rem was imprisoned in prison, no one else had seen or heard of her name. The reason why no one remembered Rem was because she was imprisoned in prison and was not publicly displayed, so no one had seen her before.
Maybe it's a way to attract the audience's attention or to show the character's playfulness. But it really depends on the context and the overall theme of the anime.
Rem's character development is a big factor. She starts off as a rather reserved and somewhat self - doubting character. But as the story progresses, she grows stronger both in terms of her abilities and her self - confidence. Also, her love for Subaru is so pure and deep that it makes readers really care about her. Her design, with her blue hair and maid outfit, also gives her a distinct and memorable look.