Tried to undub...voices may be in Japanese but they're all shuffled so nothing is heard when it should be aside from movies.
edit: second try, still no luck, I hope someone will be able to make an undub.
edit 2: 5517 voice files in JP version, 5257 (9 blank) voice files in US version
edit 3 : oh, JP voices now match US lines! have to try more but for now what went wrong in the beginning of the game is fixed.
edit 4 : went to the first time we see the school grounds, everything was perfect except for one tiny line in combat when guardman A or whatever took a shot and said "take this" instead of "kurae". not a big deal if it only does that. Some line are bound to be in english (not that many) because they were new files not present in JP version. The more pressing thing however is that a lot of files had to be cut from JP version because US version did not have them. So most likely, some voiced lines in JP won't be voiced in US.
edit 5 : and of course, I can't convert my 25h+ JP savegame... :'(