Of the two men it's the 33 year old champion who will be the favourite. He's much more experienced with 32 fights under his belt, including 7 Japanese title bouts of which he has won 5. Whilst he's not been perfect in them he has only lost to fringe world class guys in the form of Omori and Ryosuke Iwasa, which scoring wins against the likes of Yu Kawaguchi, Konosuke Tomiyama, Yushi Tanaka and Tatsuya Takahashi.
In the ring Masuda is a fighter who has developed in front of our eyes. He began his career 1-2, and was 3-3 after 6 fights before falling to 14-6 in 2012 following his loss to Iwasa. Since then he has turned things around, going 11-1 in the last 4 years and really made him self a staple of the Japanese title scene. In the ring he's rugged, has solid stamina and comes to fight with an exciting aggressive style. Although not the biggest puncher he hits harder than his record suggests and his shots sting, with surprising effect, as Konosuke Tomiyama found out back in 2014. He is however 33 and has had a long hard career with some suggesting that he may be on the slide now following a number of tough wars.
Whilst plenty is known, and a lot of footage of Masuda is available, the same cannot be said of Ozawa who is an 8 year professional at the age of 29, but hasn't yet fought many fights of name value, and has next to no big name wins. Like Masuda he had an early career struggle, falling to 2-3 and later being 4-3-1. He has however rebuilt going 9-3 since the start of 2012. That might not sound great but it has included notable wins over Yuki Strong Kobayashi Yoshihiko Matsuo, twice, as he's emerged as a contender for the Japanese throne.
Ozawa is technically a decent fighter, he has nice skills and nice speed, but he has a clear lack of power having only scored 2 stoppages in 20 fights, and his toughness is also there to be questioned with the challenger having suffered 4 stoppage losses. His lack of durability will be a real issue against a fighter like Masuda who is marauding and aggressive, and although Ozawa is a decent fighter he will struggle to keep the champion off him.
Whilst Ozawa is a live under-dog here it's hard to see anything but a Masuda win, likely by stoppage in the middle section of the fight