It's the biggest new IP since Splatoon in Japan... its also a continuation and evolution of the Wii Sports/Fit spirit.
Overall Final Fantasy has moved away from what made the IP popular in Japan, its still globally one of the top IP SE has. But it's not surprising to me that Ring Fit Adventure is going to outsell it substantially in Japan. After all Final Fantasy frenchise hasn't sold over 2M in Japan in ages.
Let's not forget that Wii Fit and Wii Sports were games that sold over 2M, so the performance of Ring Fit Adventure is only surprising when viewed from the prism of its short marketing cycle and Nintendo not being able to find success with Labo.
Wii Sports launched at 176.880 & ended up with 3.724.565 sales
Wii Fit launched at 254.009 & ended up with 3.561.787 sales
Wii Fit Plus launched at 318.755 & ended up with 2.417.762 sales
Ring Fit Adventure could very well end up as high as Wii Sports and Wii Fit if a successor isn't launched in the next three years.
