Dark Kingdom
In September 2010, he beat Alexander Otsuka to win Real Japan Pro Wrestling (RJPW)'s Legend Championship. He held the title for nearly a year before dropping it to Super Tiger in July 2011. Nagai won it back from Tiger in March 2012, and again dropped it to Tiger in December. In January 2014, Nagai's appearances in Dradition became more sporadic, and he instead became a regular in All Japan Pro Wrestling (AJPW) once again, forming the Dark Kingdom stable with Kenso, which would later add Black Tiger VII, Black Tiger and Takeshi Minamino to its ranks. As Dark Kingdom, Nagai and Minamino won the All Asia Tag Team Championship in January 2015. They dropped the titles to Ultimo Dragon and Yoshinobu Kanemaru in March.