Ayumi Hamasaki Sekai - Mai Matsumuro

She was my favorite member. Seems like she left the group in order to focus on her graduation:

Quote:

Mai, Kana and Yu had shown a great improvement this few years. Now it time for Mai to "graduate" and she will be continued to learn to write lyrics.
On 7/8/2002, 10 am Japan time, this popular girl group Dream whose one of the member is "graduating" the three original members earlier reviewed that daythat it'll now be a group of 8

http://www.jpopscan.com/jpop_dream/Imfor.html

Quote:

Recently, Mai Mastsumuro resigned from the group to persue lyric writing.

http://cupped-expressions.net/dream/info_general.php

That was the info I could find. Somehow I feel there might be other reasons that weren't shown for her leaving the group. I really have no clue, but I hope this was helpful somehow.