Final Fantasy has been declining for a long time in Japan, here is a look at the mainline installment sales in the region (excluding MMO's/direct sequels).
Final Fantasy (NES, 1987)-0.52m
Final Fantasy II (NES, 1988)-0.76m
Final Fantasy III (NES, 1990)-1.39m
Final Fantasy IV (SNES, 1991)-1.33m
Final Fantasy V (SNES, 1992)-2.43m
Final Fantasy VI (SNES, 1994)-2.55m
Final Fantasy VII (PS, 1997)-3.28m
Final Fantasy VIII (PS, 1999)-3.63m
Final Fantasy IX (PS, 2000)-2.78m
Final Fantasy X (PS2, 2001)-2.73m
Final Fantasy XII (PS2, 2006)-2.33m
Final Fantasy XIII (PS3/360, 2009)-1.88m
With the exception of FFIV, each game had sold better than the previous through the first 8 installments, peaking at 3.63m for FFVIII in 1999. Every game since then has sold less the the previous with the most recent being FFXIII selling 1.88m, about half of FFVIII and the worst selling since FFIV in 1991. Can FFXV break this trend or will the series continue to decline?
When the herd loses its way, the shepard must kill the bull that leads them astray.