Officially his assignment was to assist the local company representative Kyutaro Izaki, but in fact he was supposed to be a companion and personal assistant to Eiichi Ataka, the heir of the company and talented artist who was taking piano lessons in London, as well as his wife Michiko, another classmate of his.

[3] He played his first tournament at the Japan International Championships in 1924, where he reached his first final before losing to Tsumio Takeshi.

In 1932 he and another Japanese player Jiro Sato defeated in the third round second seeded Australians Jack Crawford and Harry Hopman, and in 1934 Miki, pairing with South African Vernon Kirby eliminated in the second round Crawford and Adrian Quist who were fourth-seeded at the time.

With the Briton Dorothy Round whom he was coaching and partnering since 1931[5] Miki first reached Wimbledon quarter-finals in 1933,[6] and the next year they won the mixed doubles tournament, making Ryuki the first Japanese player in history to win a Grand Slam event.

In 1934 Ryuki Miki won his final title at the Sheffield and Hallamshire Championships against New Zealander Cam Malfroy.