Chiba's (then known as Ryōko Usui) first appearance in a women's professional shogi major title match came in 1998 when she challenged Ichiyo Shimizu for the 6th Kurashiki Tōka Cup [ja]; Chiba lost the match 2 games to 1.
[3] That same year Chiba also challenged Shimizu for the 25th Women's Meijin title, but once again lost (3 games to 1).
[6][7] Later in 2000, Chiba won her first tournament as a women's professional when she defeated Hiroe Nakai 3 games to 1 to win the 5th Kajima Cup [ja].
[11] Chiba finally won her first women's professional shogi major title in June 2005 when she defeated Nakai 3 games to none to win the 27th Women's Ōshō [ja] title.
[12][13][14] The following year, Nakai once again challenged Chiba in the 28th Women's Ōshō title match, but this time it was Chiba coming back to win Games 4 and 5 to successfully defend her title 3 games to 2.