I will shadow drop here a plugin for people that are annoyed by double buffer and game slowing down. Didn't test it too much.
It removes double buffer + automatically adjusts game speed. Removing double buffer potentially can enable framebuffer glitches (which I see with my internal 60 FPS mod), but tested it with 153.6 MHz GPU and I saw nothing, so I guess we are alright. It gives also "slight performance boost" aka less visible framedrops because of removing double buffer.
This plugin doesn't enable 60 FPS.
It's dedicated to 2.1.0 Western version.
Cannot say about compability with Japanese version.
Just put folder "0100E95004038000" to atmosphere/contents and play game.
I am working sometimes at 60 FPS plugin for last couple of years, which has some caveats that I want to start finally fix. For sure I won't be able to remove framebuffer glitches completely because doing that results in huge game hiccups and adjusting game speed is working more randomly. But I'm trying to minimize them as much as possible.
Uploaded plugin here is a derivative from my 60 FPS mod.