2004 Happenings
- 16 new albums
- 7 new groups
- 37 new singles
- 85 joined groups
- 29 left groups
- 33 new idols
- 3 new leaders
- 4 disbanded groups
- 1 graduations
- 5 ex-leaders
- 1 retirements
January 2004
- 1 Matsuura Aya releases “×3”
- 1 Maeda Yuki releases “Sarasara no Kawa”
- 3 W is formed
- 14 Shimizu Saki becomes leader of Berryz Koubou
- 14 Berryz Koubou is formed
- 21 Morning Musume｡ releases “Ai Araba IT'S ALL RIGHT”
- 25 Abe Natsumi steps down as leader of Morning Musume｡ Sakuragumi
- 25 Murakami Megumi leaves ZYX
- 25 Umeda Erika leaves ZYX
- 25 Tsugunaga Momoko leaves ZYX
- 25 Abe Natsumi leaves Morning Musume｡ Sakuragumi
- 25 Shimizu Saki leaves ZYX
- 25 Abe Natsumi leaves Morning Musume｡
- 25 Yaguchi Mari steps down as leader of ZYX
- 25 Yaguchi Mari leaves ZYX
- 25 Yajima Maimi leaves ZYX
- 25 ZYX disbands
- 25 Yaguchi Mari becomes leader of Morning Musume｡ Sakuragumi
- 28 Gotou Maki and Melon Kinenbi release “② Paint It Gold”
- 28 Matsuura Aya releases “Kiseki no Kaori Dance｡”
February 2004
- 4 Iida Kaori releases “Aegekai ni Dakarete”
- 4 Abe Natsumi releases “Hitoribocchi”
- 11 Nakazawa Yuuko releases “Genki no Nai Hi no Komori Uta / Nagaragawa no Hare”
- 11 Minimoni｡ releases “Minimoni｡ Songs 2”
- 25 Morning Musume｡ Otomegumi releases “Yuujou〜Kokoro no Busu ni wa Nara nee!〜”
- 25 Morning Musume｡ Sakuragumi releases “Sakura Mankai”
- 25 Nakazawa Yuuko , Yasuda Kei , Abe Natsumi , Gotou Maki , Matsuura Aya and Country Musume｡ release “FS5 Sotsugyou”
March 2004
- 1 Ishikawa Rika leaves Morning Musume｡ Otomegumi
- 1 Fujimoto Miki leaves Morning Musume｡ Otomegumi
- 1 Kago Ai leaves Morning Musume｡ Sakuragumi
- 1 Morning Musume｡ Otomegumi disbands
- 1 Konno Asami leaves Morning Musume｡ Sakuragumi
- 1 Niigaki Risa leaves Morning Musume｡ Sakuragumi
- 1 Iida Kaori leaves Morning Musume｡ Otomegumi
- 1 Tanaka Reina leaves Morning Musume｡ Otomegumi
- 1 Iida Kaori steps down as leader of Morning Musume｡ Otomegumi
- 1 Morning Musume｡ Sakuragumi disbands
- 1 Michishige Sayumi leaves Morning Musume｡ Otomegumi
- 1 Yoshizawa Hitomi leaves Morning Musume｡ Sakuragumi
- 1 Yaguchi Mari leaves Morning Musume｡ Sakuragumi
- 1 Ogawa Makoto leaves Morning Musume｡ Otomegumi
- 1 Yaguchi Mari steps down as leader of Morning Musume｡ Sakuragumi
- 1 Tsuji Nozomi leaves Morning Musume｡ Otomegumi
- 1 Takahashi Ai leaves Morning Musume｡ Sakuragumi
- 1 Kamei Eri leaves Morning Musume｡ Sakuragumi
- 3 Berryz Koubou releases “Anata Nashi de wa Ikite Yukenai”
- 3 Heike Michiyo releases “JECICA”
- 10 Gotou Maki releases “Maki Goto Special Edition for Hawaii”
- 10 Matsuura Aya releases “Hyacinth”
- 17 Gotou Maki releases “Sayonara no LOVE SONG”
- 31 Morning Musume｡ releases “Best! Morning Musume｡ 2”
April 2004
- 21 Minimoni｡ releases “Lucky Cha Cha Cha!”
- 24 Berryz Koubou releases “Fighting Pose wa Date ja nai!”
May 2004
- 2 Mika leaves Hello! Project
- 2 Mika steps down as leader of Minimoni｡
- 2 Mika leaves Minimoni｡
- 2 Mika retires from show business
- 9 Takahashi Ai leaves Minimoni｡
- 9 Minimoni｡ disbands
- 12 Morning Musume｡ releases “Roman〜MY DEAR BOY〜”
- 19 W releases “Koi no Vacance”
- 24 Berryz Koubou releases “Piriri to Yukou!”
- 26 Nakazawa Yuuko releases “DO MY BEST”
June 2004
- 1 Hashimoto Aina joins Hello! Project
- 1 Akiyama Yurika joins Hello! Project
- 1 Mutou Mika joins Hello! Project
- 1 Arai Manami joins Hello! Project
- 1 Yutoku Ayumi joins Hello! Project
- 1 Ooyanagi Maho joins Hello! Project
- 1 Maeda Yuuka joins Hello! Project
- 1 HelloPro Kenshuusei is formed
- 1 Noto Arisa joins Hello! Project
- 1 Ogawa Saki joins Hello! Project
- 1 Sekine Azusa joins Hello! Project
- 1 Morozuka Kanami joins Hello! Project
- 1 Sainen Mia joins Hello! Project
- 1 Mori Saki joins Hello! Project
- 1 Hashida Mirei joins Hello! Project
- 1 Okada Yui joins Hello! Project
- 1 Sawada Yuri joins Hello! Project
- 1 Furukawa Konatsu joins Hello! Project
- 1 Tanaka Anri joins Hello! Project
- 1 Oose Kaede joins Hello! Project
- 1 Sengoku Minami joins Hello! Project
- 1 Fukuda Kanon joins Hello! Project
- 1 Noto Arisa becomes leader of HelloPro Egg
- 1 Wada Ayaka joins Hello! Project
- 1 Saho Akari joins Hello! Project
- 1 Arihara Kanna joins Hello! Project
- 1 Kitahara Sayaka joins Hello! Project
- 1 Kawashima Miyuki joins Hello! Project
- 1 Okada Robin Shouko joins Hello! Project
- 1 Gotou Yuki joins Hello! Project
- 1 Maeda Irori joins Hello! Project
- 1 Aoki Erina joins Hello! Project
- 1 Okai Asuna joins Hello! Project
- 1 Korenaga Miki joins Hello! Project
- 2 Abe Natsumi releases “Datte Ikitekanakucha”
- 2 W releases “Duo U&U”
- 9 Melon Kinenbi releases “Namida no Taiyou”
- 19 Ecomoni｡ is formed
July 2004
- 7 Gotou Maki releases “Yokohama Shinkirou”
- 14 Matsuura Aya releases “YOUR SONG〜Seishun Sensei〜”
- 22 Morning Musume｡ releases “Joshi Kashimashi Monogatari”
- 22 Nakazawa Yuuko releases “Dai Nishou〜Tsuyogari〜”
- 24 Berryz Koubou releases “1st Chou Berryz ”
- 28 Iida Kaori releases “Door no Mukou de Bell ga Natteta”
August 2004
- 1 Miyoshi Erika joins Hello! Project
- 1 Aoki Erina joins HelloPro Egg
- 1 Arai Manami joins HelloPro Egg
- 1 Tanaka Anri joins HelloPro Egg
- 1 Ogawa Saki joins HelloPro Egg
- 1 Noto Arisa joins HelloPro Egg
- 1 Sawada Yuri joins HelloPro Egg
- 1 Mutou Mika joins HelloPro Egg
- 1 v-u-den is formed
- 1 Hashida Mirei joins HelloPro Egg
- 1 Sekine Azusa joins HelloPro Egg
- 1 Sainen Mia joins HelloPro Egg
- 1 Yutoku Ayumi joins HelloPro Egg
- 1 Kitahara Sayaka joins HelloPro Egg
- 1 Okai Asuna joins HelloPro Egg
- 1 Maeda Irori joins HelloPro Egg
- 1 Saho Akari joins HelloPro Egg
- 1 Ooyanagi Maho joins HelloPro Egg
- 1 Fukuda Kanon joins HelloPro Egg
- 1 Maeda Yuuka joins HelloPro Egg
- 1 Wada Ayaka joins HelloPro Egg
- 1 Mori Saki joins HelloPro Egg
- 1 Arihara Kanna joins HelloPro Egg
- 1 Gotou Yuki joins HelloPro Egg
- 1 Okada Robin Shouko joins HelloPro Egg
- 1 Akiyama Yurika joins HelloPro Egg
- 1 Hashimoto Aina joins HelloPro Egg
- 1 Furukawa Konatsu joins HelloPro Egg
- 1 Sengoku Minami joins HelloPro Egg
- 1 Oose Kaede joins HelloPro Egg
- 1 Morozuka Kanami joins HelloPro Egg
- 1 Okada Yui joins HelloPro Egg
- 1 Tsuji Nozomi leaves Morning Musume｡
- 1 Kago Ai leaves Morning Musume｡
- 1 Korenaga Miki joins HelloPro Egg
- 1 Kawashima Miyuki joins HelloPro Egg
- 4 Country Musume｡ releases “Shining Itoshiki Anata ”
- 11 Abe Natsumi releases “Koi no Telephone GOAL”
- 18 W releases “Aa Ii na!”
- 25 Berryz Koubou releases “Happiness〜Koufuku Kangei!〜”
September 2004
- 23 v-u-den releases “Koi no Nukegara”
- 23 Okada Yui leaves HelloPro Egg
- 29 Maeda Yuki releases “Nishi Shinjuku de Atta Hito”
- 30 Konno Asami leaves Country Musume｡
- 30 Fujimoto Miki leaves Country Musume｡
October 2004
- 6 Nochiura Natsumi releases “Renai Sentai Shitsu Ranger”
- 6 Nochiura Natsumi is formed
- 14 W releases “Robokiss”
- 20 Matsuura Aya releases “Watarasebashi”
- 27 Melon Kinenbi releases “Champagne no Koi”
November 2004
- 1 Tanaka Reina joins H.P. All Stars
- 1 Saitou Hitomi joins H.P. All Stars
- 1 Ootani Masae joins H.P. All Stars
- 1 Umeda Erika joins H.P. All Stars
- 1 Gotou Maki joins H.P. All Stars
- 1 Maeda Yuki joins H.P. All Stars
- 1 Michishige Sayumi joins H.P. All Stars
- 1 Ayaka joins H.P. All Stars
- 1 Abe Natsumi joins H.P. All Stars
- 1 Fujimoto Miki joins H.P. All Stars
- 1 Miuna joins H.P. All Stars
- 1 Matsuura Aya joins H.P. All Stars
- 1 Murata Megumi joins H.P. All Stars
- 1 Iida Kaori joins H.P. All Stars
- 1 Kago Ai joins H.P. All Stars
- 1 Okada Yui joins H.P. All Stars
- 1 Kamei Eri joins H.P. All Stars
- 1 Shimizu Saki joins H.P. All Stars
- 1 Yaguchi Mari joins H.P. All Stars
- 1 Ishikawa Rika joins H.P. All Stars
- 1 Yajima Maimi joins H.P. All Stars
- 1 Inaba Atsuko joins H.P. All Stars
- 1 Tsugunaga Momoko joins H.P. All Stars
- 1 Nakazawa Yuuko joins H.P. All Stars
- 1 Tokunaga Chinami joins H.P. All Stars
- 1 Yasuda Kei joins H.P. All Stars
- 1 Murakami Megumi joins H.P. All Stars
- 1 Konno Asami joins H.P. All Stars
- 1 Sudou Maasa joins H.P. All Stars
- 1 Miyoshi Erika joins H.P. All Stars
- 1 Natsuyaki Miyabi joins H.P. All Stars
- 1 Niigaki Risa joins H.P. All Stars
- 1 Ishimura Maiha joins H.P. All Stars
- 1 Takahashi Ai joins H.P. All Stars
- 1 Kumai Yurina joins H.P. All Stars
- 1 Asami joins H.P. All Stars
- 1 Nakajima Saki joins H.P. All Stars
- 1 Yoshizawa Hitomi joins H.P. All Stars
- 1 Sugaya Risako joins H.P. All Stars
- 1 Tsuji Nozomi joins H.P. All Stars
- 1 Suzuki Airi joins H.P. All Stars
- 1 Satoda Mai joins H.P. All Stars
- 1 Okai Chisato joins H.P. All Stars
- 1 Shibata Ayumi joins H.P. All Stars
- 1 Hagiwara Mai joins H.P. All Stars
- 1 Ogawa Makoto joins H.P. All Stars
- 3 Morning Musume｡ releases “Namida ga Tomaranai Houkago”
- 10 Berryz Koubou releases “Koi no Jubaku”
- 17 Gotou Maki releases “Sayonara 「Tomodachi ni wa Naritakunai no」”
- 26 Matsuura Aya and Ecomoni｡ release “Tensai! Let's Go Ayayamu”
December 2004
- 1 H.P. All Stars is formed
- 1 Morning Musume｡ , Country Musume｡ , Coconuts Musume｡ , Melon Kinenbi , Hello! Project・Kids , W , Berryz Koubou , v-u-den and H.P. All Stars release “ALL FOR ONE & ONE FOR ALL”
- 1 Melon Kinenbi releases “THE Nimaime”
- 8 Morning Musume｡ releases “Ai no Dai 6 Kan”
- 15 Morning Musume｡ releases “Morning Musume｡ EARLY SINGLE BOX”
- 22 Morning Musume｡ , Country Musume｡ , Melon Kinenbi , W , Berryz Koubou , Ecomoni｡ , v-u-den , Nochiura Natsumi and H.P. All Stars release “Pucchi Best 5”
- 29 Iida Kaori releases “Avenir〜Mirai〜”