After graduating from Aichi University as a practiced judoka in 2012 Iwamoto began training with Shinya Ishida at the Sportiva Entertainment promotion.

On March 22, 2015, Iwamoto participated at the Powerful Tag Tournament with Daisuke Kanehira where the duo was eliminated at the semifinals to Amigo Suzuki and Kazuhiro Tamura.

On February 6, 2016, at Heat-Up Iwamoto participated at the 2016 Powerful Tag Tournament this time with Minoru Tanaka where the two lost at the first round with Kazuhiro Tamura and Mineo Fujita.

His partners were Daisuke and Joji Otani; they lost at the finals to Amigo Suzuki, Masao Orihara and Ryan Upin.

On October 5 at Basara Iwamoto and his friend Fuminori Abe participated at the Iron Fist Tag Tournament but lost to Fuma and Yusuke Kubo at the first round.

However, he wouldn't make any successful defenses as he lost the title to Shuji Kondo on September 22, ending his reign after less than a month.

[11] During this time, Atsushi Aoki would unfortunately be killed in a motorcycle accident on June 3, 2019[12] and the World Junior Heavyweight Championship belt was vacated, and a tournament would be held to crown the new champion.

After four successful defenses, Iwamoto and Lee would lose the All Asia tag titles to Isami Kodaka and Yuko Miyamoto in March 23.

He would then fulfil his opportunity the next month, by defeating Susumu Yokosuka to regain the World Junior championship for the third time in July 30.