The following year, Tachikawa was admitted into Tokyo University of the Arts and studied under Margarete Julia Netke-Löwe [ja];[2] he graduated with degrees in vocal music and performance in 1954 and 1955 respectively.

That same year, he made his professional debut as Germont in a production of La traviata at the Asahi Kaikan [ja] in Osaka.

His repertoire quickly expanded, with his interpretations of Papageno in The Magic Flute, Le Dancaïre in Carmen, and Figaro in The Barber of Seville earning him exceptional praise;[2][3] the latter role won him the 1958 Mainichi Music Prize [ja].

That same year, he was chosen to be one of the soloists for the Japanese premiere of Benjamin Britten's War Requiem played by the Yomiuri Nippon Symphony Orchestra.

[6] His recording of "My Grandfather's Clock" became an enduring source of fame for Tachikawa and established the song as a classic of Japanese popular culture when it was broadcast on the NHK children's program, Minna no uta.

A second version, utilizing the same recording, but with a new animated sequence by Takeguchi Yoshiyuki [ja] was broadcast on Minna no uta in 1972.

[4] He discovered the song during his tenure as host of the Nippon Broadcasting System radio show, Aozora Wide [ja].

That summer, he embarked on a tour of Europe, which included a performance in the Vatican City and an audience with Pope John Paul II.

[4] In reminiscences for a 2012 memorial 5-CD collection of his recordings, Sagara eulogized her former colleague:[6] Allow me to say this: there is nobody in the world of [Japanese] classical music who is as big a star as Mr. Tachikawa was.