For most users, is the go-to tool. It is open-source, frequently updated, and handles the complex nuances of different Kirikiri game versions better than older utilities.
The developer changed the XOR key or used a variant like Kirikiri Z. Fix: Use KrkrExtract while the game is running. If that fails, use a hex editor to compare the XP3 header to a known working XP3 file. You may need to find a specific xp3_decryptor keyfile from the game's community. xp3 extract