At the time of his debut, he was still a university student. On 10 November, Iwata made his major debut as a member of Sandaime J Soul Brothers with the release of the group's first single, "Best Friend's Girl", which debuted at number three on the Oricon Singles Chart. On 27 September 2010, Iwata made his first public appearance as a performer of Sandaime J Soul Brothers during the Fantasy Goya-sai: Exile Tamashī (FANTASY後夜祭~EXILE魂~ FANTASY Late Night Festival ~EXILE Soul~) live performance from Exile at Toyota Stadium. Despite the objection of his parents, Iwata declined the job offer he previously got from a big company and pursued a career in the world of entertainment instead. On 18 September, at the rehearsal for Exile's Exile Live Tour 2010 'Fantasy' in Noevir Stadium Kobe, Hiro, producer of Sandaime J Soul Brothers, announced that Iwata had passed the audition and was selected as one of the performers of the group. However, as LDH announced that they wanted to revive J Soul Brothers and form Sandaime J Soul Brothers ("The Third Generation of J Soul Brothers") in July 2010, Naoki Kobayashi, the appointed leader of the new group and Iwata's friend from Twiggz Fam, invited him to participate in the audition for performers of Sandaime J Soul Brothers. Like any other normal university students, he already had a job offer from a big company in his final year of university. Iwata did not initially pursue a career in dancing. In 2009, he also participated in 2009 Mr Keio Contest, an event whose winners are determined via online voting. He joined the group after the event and used the alias Boi Twiggz as a member of Twiggz Fam. He met Krump dance group Twiggz Fam at a dance battle event held by JUN aka Twiggz, the pioneer of the Japanese Krump scene.
After his enrollment in the Faculty of Law at Keio University, Iwata joined Dancing Crew JADE, a dance club on campus, and later became its 22nd leader.
He performed publicly for the first time at the cultural festival in his senior 3, and he was so overwhelmed by the elation of dancing that he decided to quit Lacrosse and focused on dancing in university. He used "GUN" as his stage name, which is another pronunciation for the first character (岩) of his first name Iwata (岩田). Iwata started dancing ( Krumping) after seeing RIZE, an American documentary film about Clowning and Krumping. He even made it to the short list of the Japan national Lacrosse team for the AFC U-19 Championship. He chose Lacrosse because it is only available as an extra-curricular activity for high school or higher education, so he thought he could have what it took to play on the same level as everyone else. He was admitted to Keio Senior High School subsequently, and began to play Lacrosse as an extra-curricular activity. Eventually, he successfully enrolled in Keio Futsubu School (an all-male junior high school) and moved from Nagoya to Tokyo with his mother to attend it. To live up to such an expectation, he started to attend juku (" cram school") after classes when he was still in elementary school while also meeting with a tutor at home at the same time. Both his grandfather and father are graduates of Keio University, so he was expected to follow the family's tradition.
Takanori Iwata was born into an upper-class family in Nagoya on 6 March 1989.