The same situation is appearing in my Galaxy S10+.
There was no problem with Android 10, but the same situation appears after updating to 11.

The same problem is also happening on my Mi11 Ultra with Android 11 System.

The issue is with Android 11's new enforced scoped storage. The fix is really simple to implement as this app is still targetting Android 10 an exemption can be made. The app manifest needs to be updated to include:

<application android:requestLegacyExternalStorage="true" ... >

Here's the relevant links for people who actually know how to go about fixing this:

https://developer.android.com/training/data-storage/manage-all-files

https://developer.android.com/training/data-storage/use-cases#opt-out-scoped-storage

I'd also managed to fix this manually a few months ago using solely ADB commands to grant the permission, however I have since wiped my phone and forgotten how to go about doing it again.
I had thought it was running: "adb shell appops set --uid org.tvp.kirikiri2 MANAGE_EXTERNAL_STORAGE allow" was what solved it, but that no longer seems to work.

I've made a pull request which should fix the issue. This is my first time doing anything on github so I hope I've done it properly, like I said it's a very simple fix. While looking into this a bit more, as in the last 30 minutes or so, I've also learned you can fix the issue by simply running this ADB command:

adb shell cmd appops set --uid org.tvp.kirikiri2 android:legacy_storage allow

Forcing legacy storage.

Well, can I find out how we usual players can fix it? Because Android 11 is an ass, seriously. I have license on Google Play account. Developer even plan to update the app or not? (because I don't have an opportunity to use adb etc)

I heard that we could move the the folder we want to read to make the files available to the app. However, we need to find the app's root folder first. We cannot do so without root the device.....

I've made a pull request which should fix the issue. This is my first time doing anything on github so I hope I've done it properly, like I said it's a very simple fix. While looking into this a bit more, as in the last 30 minutes or so, I've also learned you can fix the issue by simply running this ADB command:

adb shell cmd appops set --uid org.tvp.kirikiri2 android:legacy_storage allow

Forcing legacy storage.

hi! i found the adb command on A13 didn't work to enable legacy storage, do you know other way to fix this?
Thanks