The following year Iwasa made 2 defence of his national title. The first came against the tough but limited Yuki Murai, an opening round stoppage and the second saw Iwasa defeating the very under-rated Kentaro Masuda in a win that looks better now than it did at the time.
Iwasa did what he needed to, often striking as a sharp puncher when Masude left gaps, he took advantage of the flaws of the challenger very well despite some messy moments when Masuda managed to make things rough. Unfortunately for Masuda the shots of Iwasa began to take control of the bout and by the end of round 5 you could see the referee keeping a close eye on the challenger who was saved, on his feet, as Iwasa began to find the target with ease.
Whilst Iwasa was viewed as a future world champion going in to this bout Masuda was seen as nothing special. He had lost 5 of his previous 19 bouts and although he was "only" 29 was seen as a man who had reached his highest point in boxing. In 2014 however Masuda, in his second Japanese title fight, managed to win the title with a very good technical decision victory over Yu Kawaguchi. As seen in this bout, despite the loss, Masuda is better than his record indicates and courtesy of his toughness he could be a handful for many domestic fighters. Iwasa however is clearly above domestic level and many still tip him to claim a world title some day down the line.