I can't provide any information about 'reincarnating into another world and opening a harem anime' because my knowledge doesn't have any information related to this topic. If you have any other questions, I'll be happy to help you.
My answer didn't seem accurate enough. There might not be many animes where the male protagonist reincarnated into another world and tested his strength to shock the school, but Kirito in the Sword God Realm might be able to meet this condition. " Sword Art Online " was an anime with a virtual reality theme. It told the story of the companions and adventures that the protagonist Kirito met in the game.
Another theme is self - discovery. The characters usually start out in a difficult situation as sex workers but through their experiences in the other world, they learn more about themselves, their strengths and weaknesses. They might find out that they are more capable than they thought in dealing with the challenges the new world throws at them. For instance, they could develop magical abilities or form unexpected alliances. Also, the theme of social change can be present. Their presence in the new world may start to change the way society views sex work or certain social classes over time.
I recommend the book "The Substitute Messenger of One Piece World" to you. The protagonist fell into the sewers while playing a game on the road and was reborn into the world of pirates. He obtained a golden finger and won many powerful prizes through the lottery. Who asked him to be an ordinary office worker in real life? He needed to earn money to use the prizes. I hope you like my recommendation. Muah ~
I'm not sure if it's exactly what you're looking for, but 'The Harlot of the Heterogeneous World' is another one. It presents a unique take on the concept. The main character, a sex worker, discovers secrets about the world she's in that are related to ancient magic and forgotten prophecies as she goes about her daily life in this strange new world.
One common trope is the protagonist getting special powers or abilities upon reincarnation. For example, in many such novels, the main character might gain magical powers that are rare or unique in the new world. Another is the fish - out - of - water situation where the protagonist has to adapt to a completely different culture and social structure. They often bring some knowledge from their previous life which gives them an edge, like knowledge of advanced medicine or technology.
An office worker had a big report to finish. Instead of working on it, he spent the whole morning looking at pictures of cute animals online. Every time he thought about starting the report, he found another adorable cat picture to look at. By lunchtime, he had a huge collection of bookmarked animal photos but not a single word written for the report.
It could be that the manga shows how the pesticide worker adapts to the strange new world, makes friends, and overcomes obstacles with his unique skills and knowledge from his past life.
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.
One popular author is Tappei Nagatsuki. He has created works in this genre that have attracted a large following. Another is Rifujin na Magonote. His novels often feature interesting reincarnation concepts and engaging storylines.