Go to your Steam Library and open up the game's main folder.



Delete everything there except the files

re_chunk_000.pak and re_chunk_000.pak.patch_001.pak *

Verify the integrity of game files.





Here is the official manual how to verify your game's files:
https://support.steampowered.com/kb_article.php?ref=2037-QEUH-3335

Wait for the triggered download to finish AND restart afterwards your PC.

Any added third party files which are not native with Monster Hunter Rise can cause various unknown issues. Authors of modifications warn their users often and strongly to disable their modifications before every game's patch for good reasons.

If one loses track and not taking the proper measures, it can be hard to track down what specifically is causing the current experienced issue. A simple uninstall and reinstall of the game will not do, as third party files are not removed by Steam automatically. And not knowing which files are foreign to the game can make people feel uncertain about taking specific steps.

This method is good for a cleanup while minimising the amount to redownload the game files.

The game is stored in the mentioned re_chunk_000.pak like a ROM for an emulator.
Steam verifys that mentioned re_chunk_000.pak file is as it should be, unmodified and uncorrupted, then it notices the other files are missing. Downloading all the missing vanilla files, with the certainty for you that nothing what will be in your game's folder is a leftover from any modification, since you deleted everything except the re_chunk_000.pak file.

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* Update Note: PC/Steam Version 12.0.0.0
With version 12.0.0.0 of Monster Hunter Rise: Sunbreak, the developers have added an additional essential game file: re_chunk_000.pak.patch_001.pak
No worries if you delete that one too. Our main focus is to keep the main file re_chunk_000.pak so we do not have to redownload the entire game.

If you want to be on the safe side: delete everything except re_chunk_000.pak as instructed above and ignore keeping re_chunk_000.pak.patch_001.pak.

Reason: in the past that file name was used for mods too. So if you unsure if the re_chunk_000.pak.patch_001.pak in your game's folder is either a mod or a native game file, just delete it and have the game redownload it. That way you can be certain.
===================================

An alternative approach would be utilising the tip I have mentioned in this guide
https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=2791694098
by keeping a screenshot of the vanilla game folder's structure and content you can tell reliably which files are foreign and might need deletion.

Often overlooked or even forgotten are popular modifications which come as extra files in a "natives" folder, PAK patches, REFramework and/or ReShade.

Your save games are not affected by this method of cleanup, as they are stored elsewhere.

For details about their whereabouts check
https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=2743342837
If you wish to reset your save games as well, you can either do it manually by starting a new game and override your previous save game slot, or manually delete the local save game folder. For the latter, make sure to deactivate Steam Cloud synchronisations for the game, so Steam will not make an attempt to restore them should it detect discrepancies within your local save game folder.

If this tip helped you, please consider giving my other guides a look
https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=2717340432
I made them all with a lot of efforts to help players having the best Monster Hunter Rise experience they can possibly have. I hope very much they are to your liking.