The Japanese directory has a "base" directory to handle advertising in the game, in it contains DLL files, with most symbol files for the proprietary framework/engine, netcode for connecting to Zoo's (or some JP site idk) servers and EVEN the game, obviously since they're not executables, you can't run them. This internal framework of the Japanese version of the game seems to one of the closest to PVZ2 or a custom version that is as formats like RSB are mentioned in it which are not mentioned in the Worldwide PC version of the game or Blitz aside from Windows 8 but not used.

fp_d.dll: Unknown, possibly a debug version of a player (FrogPlayer?).
pl.dll: Seems to be a plugin related to loading the game. Despite what it sounds like, the associated PDB and compiled libaries do NOT match this file.
pl_d.dll: Probably a debug version of above, a matching PDB and compiled libraries are provided.

-LHR