For Uchiyama the clearest advantage is his experience in world title fights. He may have fewer total fights as a professional than Kaneko but they have been as a higher level and he'll have seen more in his 21 fights than Kaneko has seen in his 24 bouts. It's certainly not common for the champion to be the "less experienced" fighter but this is one of those cases where the fight numbers, and to a lesser extend round numbers, lie.
The bout, which will be televised on Tokyo TV, will see Uchiyama attempting to defend his WBA Super Featherweight title for the 8th time and will see him in action on a 3rd successive New Years Eve. Our preview of this bout, if you've not yet read it, can be found here.