Harem anime are defined by their vast roster of potential romantic partners, and an often male lead who becomes the focal point of multiple women's interest. When Urusei Yatsura all but introduced the subgenre through characters such as Lum and Ataru Moroboshi, it kick-started a niche that has continued to grow over the years in terms of popularity and, occasionally, the number of romantic prospects.
Source：https://www.cbr.com/biggest-harems-in-anime-kamikatsu-girls-bravo/
