Hikaru Sato
In April, Yamato took part in the 2012 Junior Tag League alongside DDT Pro-Wrestling and Pancrase representative Hikaru Sato, with the two failing to advance from their round-robin block. The following July, Yamato entered the 2012 Junior Hyper League, where he finished second in his round-robin block with three wins, one draw and one loss. On July 29, Yamato first defeated Koji Kanemoto in his semifinal match and then Shuji Kondo in the finals to win the tournament. This led to a match on August 12, where Yamato defeated Kai to win the World Junior Heavyweight Championship for the first time. Before the end of the year, Yamato racked up five successful title defenses, against Minoru Tanaka, Hikaru Sato, Kenny Omega, Kaz Hayashi, and Koji Kanemoto. On January 2, 2013, Yamato lost the title to Shuji Kondo in a match, which was also contested for Kondo's GHC Junior Heavyweight Championship. The following day, Yamato bounced back by winning his second annual junior heavyweight battle royal. That same day, Yamato reunited with Hikaru Sato to formally challenge the Junior Stars of Koji Kanemoto and Minoru Tanaka for the All Asia Tag Team Championship. On January 10, Yamato and Sato held a public training session, during which they shaved each other's heads to show that they were a cohesive unit ahead of their upcoming title match. On January 26, the team, billed as "Jounetsu Hentai Baka", defeated the Junior Stars to become the new All Asia Tag Team Champions. After only a fifteen-day reign, Yamato and Sato lost the title back to Kanemoto and Tanaka on February 10. From March 30 to April 7, Yamato and Sato took part in the 2013 Junior Hyper Tag League, where they made it all the way to the finals, before losing to Burning (Atsushi Aoki and Kotaro Suzuki), whom they had defeated in their opening match of the tournament. Afterwards, Yamato set his sights on regaining the World Junior Heavyweight Championship, pinning reigning champion Yoshinobu Kanemaru on April 29 in a six-man tag team match, where he, Koji Kanemoto and Minoru Tanaka faced the Burning trio of Kanemaru, Atsushi Aoki and Kotaro Suzuki. On June 2, Yamato unsuccessfully challenged Kanemaru for the World Junior Heavyweight Championship. On June 20, Yamato announced his resignation from All Japan out of loyalty to his trainer Keiji Mutoh, who had left the promotion when Nobuo Shiraishi took over as its new president at the beginning of the month. Prior to leaving All Japan, Yamato was entered into one more storyline, where a disappointed Hikaru Sato announced his return to the promotion to take on his former Jounetsu Hentai Baka partner. On June 30, Yamato was defeated by Sato in his final All Japan match, a three-way match, which also included Kazushi Miyamoto.