It's hard to say for sure if it's popular. There are so many manga and novels out there, especially in the isekai genre. If it hasn't been widely translated or promoted, it might not be very well - known to a large audience. It could be a niche work that only certain fans of the isekai and harem sub - genres are aware of.
Well, without having read it specifically, it could be that the 'isekai meikyuu de harem o manga novel' is centered around a male protagonist who is transported to a maze in a different world. In this maze, he encounters various female characters, which form a harem around him. The story could then follow his adventures in this strange new world, trying to survive the maze while also dealing with the complex relationships within the harem. It could also involve elements of fantasy, such as magic or special abilities that the protagonist and the harem members possess.
The harem aspect means there are multiple female characters who are attracted to the MC. In these manga, the relationships can range from simple admiration to deeper emotional bonds. The female characters often have diverse personalities and abilities, adding to the complexity of the story. For instance, in 'Death March to the Parallel World Rhapsody', the harem members include a princess, an elf, etc.
There's also 'Death March to the Parallel World Rhapsody'. The MC Ichirou Suzuki is overpowered and gradually builds up a harem of various characters in the isekai setting. The story has a mix of adventure, comedy and some harem elements.
For me, 'That Time I Got Reincarnated as a Slime' stands out. The world-building and plot development are really engaging. Also, the characters have a lot of depth.
Well, it's a bit hard to pinpoint exactly which was the very first one. But some early examples could include 'El-Hazard: The Magnificent World', which had elements of the isekai genre.
Well, 'Konosuba: God's Blessing on this Wonderful World!' is a must - mention. Kazuma is reincarnated in a fantasy world and teams up with a group of misfits, including some female characters who form a sort of harem around him. It's known for its humor and unique take on the isekai genre with harem elements.
Isekai Quartet indeed has a manga. It offers a different perspective and sometimes delves deeper into the story compared to the anime. The manga can be a great companion to the animated version for fans wanting more of the Isekai Quartet world.
One popular one is 'The Rising of the Shield Hero'. It features a unique isekai setting where the protagonist is summoned to another world as the Shield Hero, and gradually forms a harem of diverse characters throughout his adventures.
One popular harem isekai light novel is 'In Another World with My Smartphone'. The protagonist is transported to a fantasy world with his smartphone and soon finds himself surrounded by various female characters. Another is 'Overlord', where the main character, Momonga, is trapped in a game world and has interactions with different female npcs that could be considered part of a harem - like situation. And 'The Rising of the Shield Hero' also has elements of harem isekai, with the main character, Naofumi, gradually gathering a group of female companions during his adventures in the isekai world.