Her debut song, Tomorrow, sold two million copies and became a blockbuster. Alone, her 3rd single, became a longtime seller as her first ballad. Other songs composed for TV ads, anime, dramas, and movies, such as Sonomama-no-kimi de ite (be as you are), Sayonara (goodbye), Takaramono (treasure), Happy Happy T Birthday, Arara-no-jumon, etc., consecutively became commercial successes. As a composer, offers numerous songs to various singers. Apart from her activities as Mayo Okamoto, the singer-songwriter, made a debut as Mayo, the pianist, on March 2, 2016 with Always Love You, a piano & instrumental album. So far, two instrumental albums have been released under Mayo, the pianist. Working simultaneously as Mayo Okamoto, the singer-songwriter, and Mayo, the pianist, celebrated her 25th anniversary as a musician on May 10, 2020.

1995年的出道曲”TOMORROW”创下200万张销量的记录。

第三首”Alone”为首个长销民谣歌曲。之后持续推出”保持现在的你””再见” ”宝物””Happy Happy Birthday””阿拉拉的咒语”等CM连结・动画・ 戏剧・电影热门主题歌曲。

除了创作歌曲外，也以作曲家的身份相当活跃。此外，除了创作歌手冈本真夜活动以外，2016年3月2日以钢琴家mayo的身份，发行钢琴专辑”always love you”至今，目前已发行过２张专辑。以创作歌手冈本真夜及钢琴家 mayo 的身份持续活动，在2020年5月10日也迎来冈本真夜出道25周年。