I can't say whether or not it's safe(don't have the game, nor am I interessted in it), and I also don't know what antivirus you use, but my initial reaction\thought is that you have an oversensitive one that errs on the side of caution. McAffee and Avast tend to do this(as they assume power users will configure the detection thresholds themselves, or make their own exceptions, and not rely on the automated scan \ isolation).
The reason why false positives happen, has to do with how files are run on a computer(any file, even pictures), and what antiviruses do. Basically, all files are a set of byte code(machine code, 1's and 0's), where the first sets dictate what type of file it is(executable, image, text, etc), and the parameters of the file(image type for example, and it's size). Antiviruses therefore scan through these bytecodes and compare it to what they consider to be 'normal byte code' for whatever it is.
This means if there are alterations to what is expected, it'll be flagged as a Trojan. Such as say, the network portion of an executable is usually at the 10 000 - 30 000 section, but in this program it's found in the 5 000 section, it's more likely it was interjected to do something else, so the anti virus then makes the assumption this was either tampered with, or malicious(since if it wasn't, the network portion would've been in the 'normal' place).
Fan translation patches etc, make alterations to the game's byte code for a various of reasons(most common to remove double spacing for characters, or increase character limit \ reduce font sizes), which again, an oversensitive fan translation will pick up on, and make it's own assumptions(Why is the font and double space made, then suddenly removed a few sections later? That's supicious).
But again, don't know anything about this game, but it is very possible this translation was just reverse engineered from the Japanese version(with approval \ permission, obviously), therefore it triggers a false positive, or simply that it uses Japanese bytecode, with a computer and antivirus, that assumes Japanese bytecode is 'abnormal'.
Some games that triggered false positives that I have on my laptop currently(as an example): Brave Souls(Bkav pro), Ligthning Warrior Reidy(Trapmine), Mirror(MaxSecure), Magic Maker(VBA32), Drakensang(Bkav pro). Bkav pro and Trapmine has difficulty with older games(it assumes older byte code is malicious by default, which is why they trigger on these games, as both Brave Souls and LWR were recompiled using the source code iirc, so no alterations\injections.