Takagi is best known for his appearances in NJPW and Dragongate (then known as "Dragon Gate"), as well as Ring of Honor (ROH), All Japan Pro Wrestling (AJPW) and the puroresu independent circuit.

He also held the IWGP Junior Heavyweight Tag Team Championship once with fellow Ingobernables member Bushi from January to March 2019.

Takagi and Kong replaced Hulk with Jack Evans, and challenged for the vacant championship against the Muscle Outlaw'z team of Naruki Doi, Masato Yoshino, and Magnitude Kishiwada, but were unsuccessful.

Takagi then teamed with Gamma and Yamato to win the newly-vacant Open the Triangle Gate Championship, defeating Naruki Doi, Masato Yoshino and Hulk.

The following day, he fought BxB Hulk to a one-hour draw in a number one contender's match for Cima's Open the Dream Gate Championship.

On July 10, doubt was already cast over his standing in Real Hazard when he stopped them and Tokyo Gurentai members from trying to give Cima an unwanted haircut.

After a brief argument, Real Hazard attacked Takagi and kicked him out of the group for showing compassion towards Hulk and Cima, but he was saved by Typhoon.

He later teamed with Dragon Kid, a Typhoon member, in the Summer Adventure Tag League Tournament, and the pair reached the final before they were beaten by Naruki Doi and Masato Yoshino.

The duo won the annual Summer Adventure Tag League Tournament in August, and then the Open the Twin Gate Championship the following month.

After returning from an injury, Takagi disbanded Kamikaze on May 13, 2011 and the following day joined forces with Masaaki Mochizuki's new stable, Junction Three, to battle Cima's Blood Warriors.

After Junction Three was disbanded in February 2012, Takagi, alongside Yamato, joined up with Dragon Gate Nex Member Chihiro Tominaga, and the debuting Super Shenlong III and formed -akatsuki- on April 19, 2012.

[14] In order to continue his battle with Mad Blankey, Takagi formed a new stable named Monster Express with Akira Tozawa, Masato Yoshino, Ricochet, Shachihoko Boy and Uhaa Nation.

[23] On January 18, 2017, Takagi, along with fellow VerserK teammates T-Hawk and El Lindaman won a special One Day 6 Man Tag Tournament, defeating Kotoka, Masato Yoshino and Ben-K.[24] Shortly after becoming a member of Blood Generation, Shingo began wrestling for Ring of Honor (ROH) in the United States.

He became one half of the ROH World Tag Team Champions alongside Naruki Doi on March 3, 2007, by beating the Briscoe Brothers in Liverpool, England.

At Wrestlemania weekend in 2008 at "Dragon Gate Challenge II" and "Supercard of Honor III", he and BxB Hulk wrestled The Age of the Fall (Tyler Black and Jimmy Jacobs), and El Generico and Kevin Steen respectively in his last two ROH appearances.

In June, Takagi returned to Ring of Honor, which was now the sister company of AEW, teaming with his Los Ingobernables de Japon teammates Hiromu Takahashi and Bushi, to unsuccessfully challenge The Mogul Embassy (Brian Cage, Bishop Kaun and Toa Liona) for the ROH World Six-Man Tag Team Championships.

[29] However, Takagi and Bushi later lost the tag team championship to Roppongi 3K (Sho and Yoh) at NJPW's 47th Anniversary Show on March 6.

[39] After defeating Satoshi Kojima at Dominion 6.9 in Osaka-jo Hall, Takagi stated his intention to move into NJPW's heavyweight division and also declared himself as an entrant for the 2019 G1 Climax.

However Takagi would get wins over Yujiro Takahashi, British Heavyweight Champion Will Ospreay, current rival Minoru Suzuki, and over eventual tournament winner Kota Ibushi.

After Ospreay defeated Kota Ibushi for the IWGP World Heavyweight Championship, Takagi would challenge him for a match at Wrestling Dontaku 2021.

[54] Takagi would make his first title defense on July 25 at Wrestle Grand Slam in Tokyo Dome after defeating Hiroshi Tanahashi.

[62] However, before the tournament began Takagi competed at AEW x NJPW: Forbidden Door, a supershow between New Japan Pro-Wrestling and American promotion All Elite Wrestling (AEW), where he teamed with Sting and Darby Allin as 'Dudes with Attitude' to defeat Bullet Club's, El Phantasmo and The Young Bucks, with Takagi pinning Phantasmo for the win.

[65] The final match between the two men took place on October 28, where Takagi once again defeated Phantasmo to retain the provisional KOPW Championship, in a New York City Street Fight.

[67] On January 4, 2023, at Wrestle Kingdom 17, Takagi competed in the New Japan Rambo, successfully lasting till the final 4 and thus advancing to the four-way match, the following night.

[68] The following night at New Year Dash, Takagi defeated Sho, Toru Yano and Great-O-Khan to win the 2023 KOPW provisional championship.

[70] The following day at The New Beginning in Nagoya, Takagi retained the provisional KOPW championship, defeated Great-O-Khan in an MMA rules match.

The title match was contested under "Ultimate Triad" rules, meaning that to win, a wrestler would have to pin, submit and knock their opponent down for a ten-count.

[76] On June 25, Takagi teamed with Bushi and Hiromu Takahashi to defeat United Empire (T. J. Perkins, Kyle Fletcher and Jeff Cobb) on the buy-in of Forbidden Door.

[81] On January 4, 2024 at Wrestle Kingdom 18, Takagi lost the NEVER Openweight Championship back to Tama Tonga, ending his third reign at 68 days.

[83] In March Takagi entered the annual New Japan Cup, defeating Yuya Uemura and Gabe Kidd to make it to the quarterfinal round.