Teratani received both her undergraduate and graduate degrees from the Tokyo University of the Arts. She then studied at the Hamburg School of Music, graduating at the top of her class in both the voice and opera departments. While still a student there, she won the Mesfield Prize,and in 1980, she received second prize in the Netherlands' Hertoogenbosch International Song Competition. Signing an exclusive solo contract with the Bremerhaven Stadttheater, she debuted as Octavia in Der Rosenkavalier, going on to sing the roles of, among others, Rosina in Il barbiere di Siviglia, Isabella in L'Italiana in Algeri, and Gretel in Hansel und Gretel. Subsequently she signed an exclusive solo contract with the Bonn Opera, and her career began to take flight. Her roles there included Bersi in Andrea Chenier, Siebel in Faust, Annio in La clemenza di Tito, Mercedes in Carmen, Suzuki in Madama Butterfly, Prince Orlofsky in Die Fledermaus, and Fenena in Nabucco. At that time she also sang many works with the Beethovenhalle Orchestra, including music by Beethoven, Bach, Mozart and Handel.
In 1990 she moved to Hamburg and expanded her repertoire to include dramatic roles such as Preziosilla in La Forza del Destino and Eboli in Don Carlos. With Germany as her base, she has continued to sing in various places in Europe; mainly at the Hamburg Opera, the Frankfurt Opera, the Bremen Opera, and the Freiburg Opera House, with appearances also at Strasburg's Opera du Rhin, the Innsbruck opera House and the Montpellier Opera House. She performed Polish composer Henryk Gorecki's world famous Symphony No.3 "Symphony of Sorrowful Songs" in Germany, USA, Holland and Japan.
Her reputation in Europe is substantiated by the illustrious conductors who have called her to sing at their batons in Japan, including Nello Santi, Eliahu Inbal, Charles Dutoit, Jean Fournet, Riccardo Chailly, Myung-Whun Chung, Ondrej Lenard, Michel Corboz, Gary Bertini, Gerhard Bosse, Seiji Ozawa, Hiroshi Wakasugi, Kazushi Ono, Eiji Oue, and Ryusuke Numajiri. She has appeared with the major Japanese orchestras, and on stages which include Nikikai, the Japan Opera Foundation, and the New National Theatre. She is said to have "an almost perfectly polished voice" and effect "utterly convincing interpretation" of her roles. Her absorption of each character, her musical precision, and her solid singing have long made her one of Japan's leading mezzo-sopranos.