During the 2011/12 season, Nagai made his AFC Champions League debut as a 74th-minute substitute for Cerezo Osaka against Chinese club Shandong Luneng on 10 May 2011.
His playing time was greatly restricted until Ferguson stood down in February and Perth Glory appointed Alistair Edwards as his replacement.
[3] On 5 July 2013 it was announced that Perth Glory and Cerezo Osaka had finally agreed to a new loan deal for Ryo to spend the 2013/14 A-League season with the Western Australian club.
[4] On 11 January 2014 Perth Glory and Nagai parted company with the Western Australian club terminating the speedy winger's loan contract.
Nagai was unable to participate in the remainder of the A-League season after suffering a serious hamstring tear in Perth's round 11 0–0 draw with Adelaide United.