1998 Happenings
- 13 born
- 3 new albums
- 9 new singles
- 1 new groups
- 4 joined groups
- 3 new idols
January 1998
- 28 Morning Musume｡ releases “Morning Coffee”
February 1998
- 15 Heike Michiyo releases “Sotsugyou〜TOP OF THE WORLD〜”
March 1998
- 12 Yasuda Kei joins Hello! Project
- 12 Yasuda Kei joins Morning Musume｡
- 12 Ichii Sayaka joins Morning Musume｡
- 12 Yaguchi Mari joins Hello! Project
- 12 Yaguchi Mari joins Morning Musume｡
- 12 Ichii Sayaka joins Hello! Project
- 25 Heike Michiyo releases “Teenage Dream”
April 1998
- 3 Ootsuka Aina is born
- 6 Katsuta Rina is born
May 1998
- 14 Horie Kizuki is born
- 27 Morning Musume｡ releases “Summer Night Town”
- 28 Sayashi Riho is born
June 1998
- 12 Murota Mizuki is born
July 1998
- 1 Heike Michiyo releases “Daikirai”
- 8 Morning Musume｡ releases “First Time”
- 28 Okamura Rise is born
August 1998
- 5 Nakazawa Yuuko releases “Karasu no Nyoubou”
- 5 Suzuki Kanon is born
- 28 Mikame Kana is born
September 1998
- 9 Morning Musume｡ releases “Daite HOLD ON ME!”
October 1998
- 5 Nakazawa Yuuko becomes a soloist
- 18 Tanpopo is formed
- 25 Heike Michiyo releases “Dakedo Aishisugite (single Ver)”
- 30 Tamura Meimi is born
November 1998
- 5 Ogata Risa is born
- 18 Tanpopo releases “Last Kiss”
- 24 Yamagishi Riko is born
December 1998
- 1 Miyamoto Karin is born
- 2 Nakazawa Yuuko releases “Odaiba Moonlight Serenade”
- 12 Nakazawa Yuuko releases “Nakazawa Yuuko Dai Isshou”
- 30 Uemura Akari is born