Year 24 Group (24年組 Nijūyo-nen Gumi) is a label applied by critics and fans to a nebulous group of female manga artist considered to have revolutionized shōjo manga (girls' comics) in the 1970s. Their works often examine "radical and philosophical issues," including sexuality and gender issues, and many of their works are now considered "classics" of shōjo manga. The name Fabulous Year 24 Group (花の24年組 Hana no Nijūyo-nen Gumi), comes from the fact that manga artists said to belong to this group were generally born around Shōwa 24 (1949). The origin of the term is unknown. In English, they have also been called the "Magnificent Forty-Niners." The exact membership is not precisely defined, but the three artists most often mentioned by critics or scholars as possible members are Moto Hagio, Yumiko Ōshima, and Keiko Takemiya. Other artists who have been included in a list include Toshie Kihara, Ryoko Yamagishi, Minori Kimura, Riyoko Ikeda, Nanae Sasaya, and Mineko Yamada.
Toku argues that the Year 24 Group significantly contributed to the development in shōjo manga of such sub-genres as "Sci-Fi, Love, History, Adventure," while Matsui notes the prevalence of bildungsroman genre conventions in their works. Stylistically, the Year 24 Group created new conventions in panel layout by departing from rows of rectangles that were the standard of the time and using panel shape and configuration to convey emotion, and softening or removing panel borders.
Moto Hagio and Keiko Takemiya lived in the same apartment in Ōizumi in Nerima, Tokyo from 1970 to 1973, in a situation similar to Osamu Tezuka's Tokiwa-so. Takemiya's friend Norie Masuyama lived nearby and was described by Moto Hagio as Takemiya's "brain staff." Masuyama was not a manga artist herself, but she introduced Takemiya to male homosexuality for women via Barazoku, which inspired Takemiya and Hagio to create shōnen-ai works.