She combines Occidental tradition and the Asiatic sense of breathing in a style of 'magical' rhythms and unusual sounds of great formal and stylistic freedom. Her catalogue (published by Breitkopf & Härtel) consists of about 40 titles, including 15 symphonic compositions and 12 pieces for ensemble. Her works, which have been performed at international festivals such as the Salzburg Festival, the Biennale di Venezia, and the Folle Journée in Tokyo, have received numerous awards: the audience prize at the Festival Ars Musica in Brussels for Chimera in 2002; the Japanese State Prize for the greatest young artistic talent in 2003; the Otaka Prize for the best symphonic world premiere in Japan in 2005 (for Cloud Nine); the Grand Prize of the Tribune internationale des compositeurs in 2008 (for L'heure bleue); and the Heidelberg Women Artists' Prize in 2010. Her most outstanding productions include the orchestral portrait concert at Suntory Hall in Tokyo (2007), the cinema concert at the Louvre with the music to the silent film Le fil blanc de la cascade by Kenji MIzoguchi (2007), and the portrait concert at the Festival d'Automne in Paris (2010).
Between 2011 and 2013 Mochizuki was composer-in-residence at the Festival international de musique de Besançon. Since 2007 she has been professor of artistic disciplines at the Meiji Gakuin University in Tokyo, and has been invited to give composition courses in Darmstadt, in Royaumont, in Takefu, at the Amsterdam Conservatory, and others. Within the framework of her activities, she continually reflects on the role of the composer in today's society and on the necessity to open oneself to it. In addition, she writes a column about music and culture for the renowned Yomiuri Shimbun, the most widely read daily newspaper in Japan.