Reverse harem

Harem (ハーレムもの, hāremumono; "from harem") in anime and manga is an emphasis on polygamous or love triangle relationships characterized by a protagonist surrounded amorously by three or more members of either the same and/or opposing gender, sex, and/or love interests. When it is a yuri or male-hetero oriented harem series, the polygynous relationship is informally referred to as a female harem or seraglios. When it is a yaoi or female-hetero oriented harem series, the polyandrous relationship is informally referred to as a male harem, reverse harem, or gyaku hāremu (ハーレム).

The word derives from Harem, which was a term used to refer to the most private rooms of a household in the Islamic world, especially among the upper class where only women and close relatives were permitted inside.

Because romance is rarely the main focus of an entire series, a harem structure is ambiguous. The most distinguishable trait is the group of polyamorous females and/or males who accompany the protagonist; in some instances cohabitate with the protagonist. While intimacy is just about customary, it is never necessary. When it is present, it is always a minimum of three supporting characters who express romantic interest in the protagonist.

With characters such as Haruhi Fujioka (Host Club) and Keima Katsuragi (The World God Only Knows) being the rare few exceptions, the main "love interest" protagonists of any "harem" anime, manga or video game, are rarely given much focus or character development. These characters are "blank slates" meant to literally allow the reader, player, or viewer to pretend they're the protagonist and apply their own personality. Harem protagonists are designed to make females and/or males within the "harem" more attractive while highlighting interesting aspects of their personalities, usually because of said protagonist's kindness, courage and the will to protect/support their friends.

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Wikipedia