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Saya no Uta Remastered .NPK Repacking Problem

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This game has a ridiculous number of releases, which makes sense given its age. Which version do you have that has that .npk file?

There are other versions like this one that do not have .npk files and are playable via various interpreters. I have not found one for Windows, but I also have not looked very hard. It seems to be an The text files are in plain text as well.

Different releases use different game engines, so it might be worth checking out the other ones unless you have a particular reason to prefer the release that has the .npk. What are the reasons to use that one?

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Okay some more background information about this problem just to try to make sense of everything.

- For the remastered version developed by Nitroplus, it is available on both Steam and JAST USA.
- The steam version was released on Aug, 12, 2019, and it also has a Chinese localization by Kagura Games. Not sure about the JAST version.
- On Aug 13, 2019, JAST released a free update patch for the original Saya no Uta that supposedly changes/changed the game to the remastered version including the game engine. Compared to the original, JAST says the remastered has better CGs, a better translation,  Win10 compatibility, and an obnoxious script.npk format on a new game engine. Maybe it is the same engine but they updated the game engine version? I have not tested JAST's upgrade patch to test JAST's claims yet, but might later.
- JAST says the release version is May 05, 2013, but it is not clear if this date is for JAST's original localization of Saya no Uta or for the remastered version. Probably this is the release date for their original version, but I am not sure.
- VNDB says the game engine for the new remastered version is Diesel Engine of which there are quite a few translations available, but I have not looked through that list to see if any of those translation involve unofficial patches yet. If they do, then that is proof that some method already exists to patch the game engine to load custom scripts.
- Both Steam and JAST's remastered versions use the same .npk format to pack the script.npk file indicating they are likely both on same game engine version despite any superficial differences in marketing.
- However, those superficial differences in the game engine are a substantial difference in content since the Steam version is censored because Steam. JAST has a DLC/patch available to fix the Steam version. In other words, the Steam release should be avoided due to censorship, which is pretty typical of Steam + VNs in general.
- Garbro recognizes this *.npk format and, besides none, has 3 existing decryption schemes for it, Minikui Mojika no Ko, Sonicomi, Tokyo Necro, but nothing works on the script.npk file.
- There is this person on steam that claims 'It's possible to patch the game, since it uses the same NPK2 archive format that Tokyo Necro and Sonicomi uses. The only thing is, the encryption must be cracked.' -Exciel
- The ascii/string header for the script.npk file in a hex editor is NPK2, 4E 50 4B 32 02 00 00 00 , or NPK2 'STX'.

- The next step towards developing a patch for the remastered version is to look through the Diesel Engine list to see if any version has an unofficial patch available for the script files.
- Then either 1) obtain the Diesel Engine and see if it can unpack the script.npk file or 2) reverse engineer the obfuscation and or encryption in the script.npk to unpack it. Repacking should be possible by using the original game engine, or just reverse engineering that packing process too.

The alternative way to patch this game is to use the original version instead, which seems to be fully open source?, instead of the remastered version that uses .npk. Besides CGs, there does not appear to be any major content differences. The difference in translation quality does not matter if translating it again. The Win 10 compatibility thing seems more like a marketing gimmick that should be easily fixable for the original version somehow.

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