A native of Japan, mezzo-soprano Yumi Koyama holds both Bachelor and Master of Fine Arts degrees from the Tokyo National University of Fine Arts and Music. She went to Germany and sung sacred music in Munich, Leipzig and other German cities.
 She was selected for Eboli in Schleswig-Holstein Musik Festival, Laura in Tchaikovsky's Ioranta in Salzburg.
 In modern music field she recorded on a lot of TV and radio programs in US, Paris and Germany.
 In Tokyo she made her Nikikai Opera-debut as Fricka in Die Walküre in 1996 and made New National Theatre Tokyo debut as Ortrud in Lohengrin in 1997, and sang Venus in Tanhäuser at Nikikai Opera in 1999. She was given high praises through these performances.
 She sang in Die Walküre conducted by Sinopoli in Rome in 1999, after that she made her Bayreuth debut as Rossweise in Die Walküre conducted by Sinopoli in 2000. Since then she had sung in Bayreuth every five year until 2004.
 She sang in Das Rheingold, Walküre, Lohengrin in Tokyo City Philharmonic Orchestral Opera Series and contributed greatly to the success of these performances.
 She has also been a popular performer on concert stages. She made a great success as a mezzo-soprano soloist in Stabat Mater (Rossini) conducted by C.Dutoit with NHK Symphony Orchestra, in Symphony no.9 (Beethoven) conducted by J.Märkl with NHK Symphony Orchestra, in Resurrection (Mahler) conducted by C.Myung-Whun with Tokyo Philharmonic Orchestra.
 Now she resides in Stuttgart. She is a member of Nikikai.