On November 11, 2012 Tanaka made his pro wrestling debut in the opening match of the NEVER: Shodai NEVER Musabetsu Kyu Oza Kettei Tournament 1st round show where he lost to Takaaki Watanabe.
Tanaka competed as one of NJPW's "Young Lions" a class of rookie wrestlers who work mostly against each other early on, wearing all black gear and with no particular ring character, all part of the structured learning process in NJPW.
Throughout 2013 and 2014 Tanaka often faced off against fellow Young Lion Yohei Komatsu, with both men trading victories in both singles and tag team competition.
By 2015 Tanaka and Komatsu had begun teaming together on a regular basis, including working together in the New Japan Rumble as part of Wrestle Kingdom 9 on January 5, 2015.
The two teamed up to eliminate Tiger Mask and Taichi but were both eliminated by Tama Tonga Tanaka was called upon to replace an injured Rey Cometa on a NJPW/Consejo Mundial de Lucha Libre co-promoted Fantastica Mania 2015 show on January 14.
Tanaka and Stigma lost to La Peste Negra ("The Black Plague"; Bárbaro Cavernario and Mr. Niebla) On February 11, 2015 Tanaka defeated rival and occasional tag team partner Yohei Komatsu in the opening match of NJPW's 2015 The New Beginning in Osaka show.
In June and July 2015 Tanaka represented NJPW in Pro Wrestling Noah's Global Junior Heavyweight League.
During the tournament he earned two points by defeating Hitoshi Kumano but lost to Daisuke Harada, Zack Sabre Jr. El Desperado, Kenoh and Yoshinari Ogawa to be eliminated from the tournament.
At the 2015 Destruction in Kobe show Tanaka and Komatsu defeated fellow Young Lions David Finlay and Jay White.

In early 2016 it was announced that Tanaka and Komatsu would compete in the 2016 Fantastica Mania series of shows, competing in what NJPW called the "Yohei Komatsu and Sho Tanaka send-off game", announcing that the two would travel to Mexico and work for CMLL as part of their continued in-ring skill development.
The team worked the opening match for each of the six Fantastica Mania events, losing each time.
On November 11, 2012 Tanaka made his pro wrestling debut in the opening match of the NEVER: Shodai NEVER Musabetsu Kyu Oza Kettei Tournament 1st round show where he lost to Takaaki Watanabe. Tanaka competed as one of NJPW's "Young Lions" a class of rookie wrestlers who work mostly against each other early on, wearing all black gear and with no particular ring character, all part of the structured learning process in NJPW. Throughout 2013 and 2014 Tanaka often faced off against fellow Young Lion Yohei Komatsu, with both men trading victories in both singles and tag team competition. By 2015 Tanaka and Komatsu had begun teaming together on a regular basis, including working together in the New Japan Rumble as part of Wrestle Kingdom 9 on January 5, 2015. The two teamed up to eliminate Tiger Mask and Taichi but were both eliminated by Tama Tonga Tanaka was called upon to replace an injured Rey Cometa on a NJPW/Consejo Mundial de Lucha Libre co-promoted Fantastica Mania 2015 show on January 14. Tanaka and Stigma lost to La Peste Negra ("The Black Plague"; Bárbaro Cavernario and Mr. Niebla) On February 11, 2015 Tanaka defeated rival and occasional tag team partner Yohei Komatsu in the opening match of NJPW's 2015 The New Beginning in Osaka show. In June and July 2015 Tanaka represented NJPW in Pro Wrestling Noah's Global Junior Heavyweight League. During the tournament he earned two points by defeating Hitoshi Kumano but lost to Daisuke Harada, Zack Sabre Jr. El Desperado, Kenoh and Yoshinari Ogawa to be eliminated from the tournament. At the 2015 Destruction in Kobe show Tanaka and Komatsu defeated fellow Young Lions David Finlay and Jay White.
In early 2016 it was announced that Tanaka and Komatsu would compete in the 2016 Fantastica Mania series of shows, competing in what NJPW called the "Yohei Komatsu and Sho Tanaka send-off game", announcing that the two would travel to Mexico and work for CMLL as part of their continued in-ring skill development. The team worked the opening match for each of the six Fantastica Mania events, losing each time.
Sho Tanaka