Anal sex is a prevalent theme in yaoi, as nearly all stories feature it in some way.The storyline where an uke is reluctant to have anal sex with a seme is considered to be similar to the reader's reluctance to have sexual contact with someone for the first time.Although seme and uke roles are already used in some manga to describe which member of the relationship is more dominant and which member is more passive, there are just as many manga novels which subtly or overtly differentiate between the two.A gay male who asks out another male can initiate the relationship but also enjoy the sensation of being a bottom in anal sex.In the late 1970s, shōjo magazines devoted to the new genre began to appear; and, in the 1990s, the term boys' love or BL was invented for the genre, which replaced earlier terms such as tanbi, shōnen ai and juné in Japanese usage.In Japan, the term yaoi continues to refer mainly to parody dōjinshi; among Western fans, however, yaoi is used as a generic term for female-oriented manga, anime, dating sims, novels and fan fiction works featuring idealized gay male relationships.Female authors writing for shōjo (girl's) manga magazines in the early 1970s published stories featuring platonic relationships between young boys, which were known as tanbi (aesthetic) or shōnen ai (boy love).In the late 1970s going into the 1980s, women and girls in the dōjinshi (fan fiction) markets of Japan started to produce sexualized parodies of popular shōnen (boy's) anime and manga stories in which the male characters were recast as gay lovers.
Seme and uke is similar but not identical to tachi and neko because the former refers primarily to sexual roles, whereas the latter describes personality.
The term shōnen-ai (boy love) originally connoted ephebophilia or pederasty in Japan, but from the early 1970s to the late 1980s, was used to describe a new genre of shōjo manga, primarily produced by the Year 24 Group of women authors, about beautiful boys in love.
Characteristics of shōnen-ai include exoticism, often taking place in Europe, Jeffrey Angles particularly notes Moto Hagio's The Heart of Thomas (1974) and Keiko Takemiya's Kaze to Ki no Uta (1976–1984) as being groundbreaking, noting their portrayal of intense friendship between males, including jealousy and desire.
Although the yaoi genre is also called Boys' Love (commonly abbreviated as BL), the characters may be of any age above puberty, including adults.
Works featuring prepubescent boys are labelled shotacon and seen as a distinct genre.