Well, a typical theme in such novels is friendship. The protagonist usually makes new friends in the other world who help them on their journey. Magic and the supernatural are also common themes. There are different magical systems, and the characters often have to deal with magical creatures or phenomena. And there's the theme of the unknown. The new world is full of things they don't understand, which drives the story forward.
Yeah, it's popular. There are so many fans of this kind of web novel. People are often attracted by the unique settings in these stories, like strange races, powerful magic systems, and epic adventures in the other world. It gives readers a chance to escape from the real world and immerse themselves in a fictional and exciting world.
There are many anime works that transmigrate to another world. The following are some examples:
1.<< Index of Forbidden Magic Books >>: The main character, Dang Ma, became a mage after crossing over to another world.
2." Tokyo Ghoul ": The protagonist Kim Mu-yan accidentally transmigrated to another world and became a ghoul.
[3. The Blade of Ghost Destruction: The protagonist, Tanjiro, is an ordinary office worker who accidentally transmigrated to another world and became a Ghost Hunter.]
4." Sword God Realm ": The protagonist, Kirito, was a gamer who traveled to another world in a game and became an adventurer.
5." About Me Reincarnating into a Slime ": The protagonist reincarnates into a slime and begins his adventure in the Otherworld.
These are just some of the works. In fact, there are many other works that you can choose according to your preferences.
The more common types of anime where siblings transmigrated to another world were fantasy or science fiction. In such novels, there would usually be a pair of siblings who, for some reason, traveled to another world and experienced various adventures and challenges in that world. They might encounter all kinds of magical creatures and magic, as well as all kinds of powerful enemies, but they would definitely be able to overcome all kinds of difficulties and become the strongest in the other world. This type of novel often had exciting plots and exciting battle scenes that were deeply loved by readers.
There were many cartoons about traveling to other worlds, some of which included:
1 Sword God Domain: It tells the story of a game player who transmigrated to another world to fight and adventure with other players.
2.<< Index of Forbidden Magic Books >>: It tells the story of the protagonist, Tama Shangjo, who traveled to another world to fight and adventure with various superpowers.
[3]" The Attacking Giant ": It tells the story of the protagonist, Alan, who has traveled to another world to fight and survive with other humans and giants.
4.<< Re-Life in a foreign world from scratch >>: It tells the story of a programmer who transmigrated to a foreign world to fight and grow with various monsters and characters.
5. The Ghost Blade: It tells the story of the protagonist, Tanjiro, who traveled to another world to fight and grow up with various demons and ghosts.
There were many animes that had infinite rebirth in the foreign world. Among them, the more well-known ones were Sword God Realm, Gate of the Fate Stone, Attack of the Giant, Forbidden Magic Book Catalog, Tokyo Ghoul, and so on. These works all involved the elements of the foreign world and rebirth, telling the stories of human adventures, battles, and survival in the foreign world. Among them, the Sword God Realm and the Stone of Destiny Gate were the more popular works. Not only did they have exquisite animation production, but they also involved a lot of scientific and philosophical knowledge, which was deeply loved by the audience.
Well, in many of these novels, there are strong female characters. Take Tanya from 'The Saga of Tanya the Evil'. She is a very complex and powerful character. Then there are the loyal knights or warriors. They are often by the side of the protagonist, protecting them and fighting alongside them. And let's not forget about the mysterious and alluring elves that are frequently found in 'isekai tensei recruited to another world novel' settings.
One common theme is self - improvement. The protagonist, who is often reborn or transported, has to quickly adapt and grow stronger in the new world. Another theme is exploration. They explore the new world, its cultures, and its secrets. Also, there is often a theme of heroism, where the protagonist becomes a hero in the new world.
There are many harem animes where the male protagonist goes to another world. The following are some of the recommendations:
"Sword God Realm": The story of the male protagonist Kirito accidentally transmigrated to the virtual reality world and established a harem relationship with other characters.
2.<<Forbidden Magic Book Catalog>>: It tells the story of the male protagonist, Doma Shangjo, who transmigrated to the world of the Forbidden Magic Book Catalog and established a harem relationship with other characters.
3. Fate/Zero: The story of the male protagonist Shiro transmigrating into the Fate/stay night world and establishing a harem relationship with other characters.
4 "Life in a different world from scratch": It tells the story of the male protagonist Rem who transmigrated to a different world and established a harem relationship with other characters.
5 "Life in a different world from scratch II": The story of the male protagonist Rem continuing to transmigrate to another world and establishing a harem relationship with other characters.
The above are some recommendations. I hope you are satisfied.