On 13 August 2013, Miyaichi was registered as a Specially Designated Player.[2]
Tsuyoshi Miyaichi was signed by Shonan Bellmare in 2014.[3] He made his league debut against Tokyo Verdy on 31 May 2014.[4] On 6 December 2018, it was announced that Shonan Bellmare would not be renewing his contract.[5]
In 2018, Miyaichi moved on loan to Grulla Morioka.[11] He made his league debut against Gamba Osaka U-23 on 11 March 2018.[12] Miyaichi scored his first league goal against Cerezo Osaka U-23 on 7 July 2018, scoring in the 13th minute.[13]
Iwate Grulla Morioka
On 8 January 2019, Miyaichi was announced at Iwate Grulla Morioka.[14] He made his league debut against Roasso Kumamoto on 31 March 2019.[15] Miyaichi scored his first league goal against Azul Claro Numazu on 9 June 2019, scoring in the 36th minute.[16] On 15 December 2020, Miyaichi's contract was renewed and he was diagnozed with Osgood syndrome.[17]