The top 6 airlines in Japan by fleet size are:
ANA / ANA Wings 251
JAL / JAL Express 156
Air Japan 32
Sky mark 31
J Air 22
Jetstar Japan 17
It's credible that Jetstar Japan carried more passengers than J Air as they only operate a fleet of smaller regional jets.
I find it hard to believe JQ carried more pax then either Air Japan or Skymark considering some of their 17 aircraft are operational spares.
MC.