2005 was the year that ℃-ute was formed, Kusumi Koharu joined Morning Musume, Ishimura Maiha graduated from Berryz Koubou and Hello! Project, Iida Kaori and Ishikawa Rika graduated from Morning Musume and Yaguchi Mari resigned from Morning Musume.
- January 30:
- March 8: Shutto Anna was born.
- April 14:
- May 1: Kusumi Koharu joins Morning Musume
- May 7: Ishikawa Rika graduates from Morning Musume
- May 9: Okamura Homare was born.
- June 11: ℃-ute is formed
- June 28: Yamazaki Mei was born.
- July 7: Matsunaga Riai was born.
- July 15: Yamada Ichigo was born.
- July 20: Nakayama Natsume was born.
- July 15: Yamada Ichigo was born.
- August 30: Ooyanagi Maho leaves Hello Pro Egg
- September 2: Kanemitsu Ruru was born.
- September 14: Kawashima Miyuki graduates from Hello Pro Egg
- October 2: Ishimura Maiha graduates from Berryz Koubou and Hello! Project
- October 6: Hashisako Rin was born
- January 9: Ran・RUN・Ran - Heike Michiyo
- January 19: THE Manpower!!! - Morning Musume
- February 9:
- February 23: Zutto Suki de Ii desu ka - Matsuura Aya
- March 2: Kacchoii ze! JAPAN - v-u-den
- March 30: Special Generation - Berryz Koubou
- April 20: Yume Naraba - Abe Natsumi
- April 27: Osaka Koi no Uta - Morning Musume
- May 18: Ai no Imi wo Oshiete! - W
- May 25: Ajisai Ai Ai Monogatari - v-u-den
- June 8: Nanchuu Koi wo Yatteruu YOU KNOW? - Berryz Koubou
- June 22: Onna, Kanashii, Otona / Inshouha Renoir no You ni / Hitoshirezu Mune wo Kanaderu Yoru no Aki - Sexy Otonajan, Elegies, Puripuri Pink
- July 6: Suppin to Namida. - Goto Maki
- July 27: Iroppoi Jirettai - Morning Musume
- August 3: 21ji Made no Cinderella - Berryz Koubou
- August 10: Hitorijime - v-u-den
- August 31: Koi no Hana - Abe Natsumi
- September 7: Miss Love Tantei - W
- September 21: Ki ga Tsukeba Anata - Matsuura Aya
- October 5: Kurenai no Kisetsu - v-u-den
- October 19: Suki Sugite Baka Mitai - DEF.DIVA
- November 9: Chokkan 2 ~Nogashita Sakana wa Ookiizo!~ - Morning Musume
- November 23: Gag 100kaibun Aishite Kudasai - Berryz Koubou
- November 30: Takaramono - Abe Natsumi
- December 9: unaffected - Heike Michiyo
- February 23: 3rd Station - Goto Maki
- February 28: Koimizuki - Heike Michiyo
- March 2: 2nd W - W
- March 24: Matsuura Aya Best 1 - Matsuura Aya
- May 27: Mika - Mika Todd (debut)
- October 26: Suite Room Number 1 - v-u-den (debut)
- November 16: Dai ② Seichouki - Berryz Koubou
- December 7: Special! Best Mini ~2.5maime no Kare~ - Berryz Koubou
- December 21:
- December 24: Goto Maki Premium Best 1 - Goto Maki
- August 3: Event V "Berryz Koubou Ikube~"
- January 3: Morning Musume Iida Kaori Graduation Memorial
- March 3: Morning Musume DVD MAGAZINE Vol.3
- April 9: Morning Musume Ishikawa Rika Sotsugyou Memorial
- August 20: Morning Musume DVD MAGAZINE Vol.4
- October 15: Morning Musume DVD MAGAZINE Vol.5
- January 6: 50W - W
- Feburary 22: Ogawa Makoto (photobook) - Ogawa Makoto
- February 25: Real 226 - Fujimoto Miki
- March 4: Hello!x2 Miyoshi Erika & Okada Yui from v-u-den Miyoshi Erika & Okada Yui
- March 24: A - Matsuura Aya
- April 26: Dear... - Goto Maki
- May 19: Berryz Koubou (photobook) - Berryz Koubou
- May 26: Fu - Abe Natsumi
- June 25: Ai Gokoro - Takahashi Ai
- July 1: Ishikawa Rika Shiawase no Ashiato Happpy! - Ishikawa Rika
- August 10: Natsufuku ~Natsu wo Sugosu Shoujo~ - Konno Asami
- September 2: Alo-Hello! Abe Natsumi' - Abe Natsumi
- September 16: DAYS - Kamei Eri
- October 15: Reina - Tanaka Reina
- November 16: Angels - Ishikawa Rika & Michishige Sayumi
- December 17: Cheri - Fujimoto Miki
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