Born 20th January, 1983, Mari Yaguchi (矢口真里) has been one of the most versatile but underrated members of the Hello! Project.

She became a member of Morning Musume during the second generation auditions, but resigned suddenly in April 2005, basically citing her desire to move on "as an adult" with her career. Her TV show Yaguchi Hitori continues as before, and her first post-Morning Musume solo release is in the works.