Japanese champion

Iwata was expected to face Rikito Shiba for the vacant Japanese light-flyweight title on 11 September 2021, at the Korakuen Hall in Tokyo, Japan. The fight had to be postponed the day before however, as Iwata tested positive for COVID-19 after successfully making weight.^[14] The title bout was postponed for 5 November 2021.^[15] Iwata won the first ten-round fight of his career by a ninth-round technical knockout. He knocked Shiba down in the sixth round, and appeared to once again knock him down in the eight round as well, although the second knockdown was ruled a slip by referee Tetsuya Iida. Immediately after action resumed in the ninth-round, Iwata forced Shiba back with a flurry of punches which forced the referee to wave the fight off.^[16]

Iwata was booked to make his first Japanese light-flyweight title defense in a rematch with Toshimasa Ouchi. The fight was scheduled as the headliner of the March 5, 2022, "Dynamic Glove" event, and was broadcast by G+.^[17] Iwata won the fight by a first-round knockout, flooring Ouchi with a counter right hand. Although Ouchi was able to rise from the canvas in time, he was unsteady on his feet, which prompted the referee to wave the bout off.^[18] Iwata was awarded the MVP award for the month of March by the East Japan Boxing Association, following this victory.^[19]

Japanese, WBO AP and OPBF champion

Iwata was booked to make his second Japanese title defense in a title unification bout with the OPBF light-flyweight champion Kenichi Horikawa at the Korakuen Hall on July 2, 2022. Aside from the Japanese and OPBF titles, the vacant WBO Asia Pacific title will be contested as well.^[20] Iwata won the fight by unanimous decision, with scores of 118–110, 117–111 and 116–112.^[21] He was given the July "Fighter of the Month" award by the East Japan Boxing Commission following this victory.^[22] On August 19, 2022, the Japanese Boxing Association gave him the "Skill Award" for the year 2022.^[23]

Iwata vs. González

On 3 September 2022, it was announced that Iwata would challenge the reigning WBO light flyweight champion Jonathan González. Their fight was scheduled as the co-main event of the Kenshiro Teraji and Hiroto Kyoguchi light flyweight unification bout, which took place on 1 November 2022.^[24] He lost the fight by unanimous decision, with two scorecards of 116–112 and one scorecard of 117–111.^[25]