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Installing KRFN Client (iOS)

This guide describes how to install KRFN v3.6.0 on an iOS device. Because the game is offline and no longer available on the modern App Store, we will use a legacy version of iTunes along with Fiddler Classic to intercept the download request and downgrade the client to v3.6.0.

Warning

Proceed at your own risk. You must disable automatic app updates on your iOS device to prevent the app from being overwritten. (Using a dedicated testing device is highly recommended.)

Workflow Overview

To give you a quick visualization of the process, here is the complete flow from setting up your environment to modifying the App Store request and syncing the client:

flowchart TD
    Start["Start Process"] --> Prep["1. Prepare PC (Uninstall modern iTunes & install legacy iTunes / Fiddler)"]
    Prep --> Login["2. Log in to iTunes & locate KRFN on Purchased page"]
    Login --> Breakpoint["3. Set Fiddler Breakpoint ('Before Requests')"]
    Breakpoint --> Trigger["4. Click download icon (Cloud) in iTunes"]
    Trigger --> Intercept["5. Intercept '/buyProduct' request in Fiddler"]
    Intercept --> Modify["6. Modify 'appExtVrsId' value to 854995007"]
    Modify --> Resume["7. Resume request to download v3.6.0 IPA"]
    Resume --> Sync["8. Connect iOS Device and sync IPA via iTunes"]
    Sync --> Done["Success! Client v3.6.0 installed on iOS"]

Prerequisites

Before starting, ensure you have the following assets and environments ready:

1. Windows PC (Without Modern Apple Software)

If you already have modern iTunes or other Apple software installed via the Microsoft Store or standard installers, you must completely uninstall them first to prevent library conflicts. Please uninstall:

  • Apple Mobile Device Support
  • Apple Software Update
  • iTunes (along with deleting the folder C:\Users\<username>\Music\iTunes)

2. Apple ID with Purchase History

You must use an Apple ID that has previously downloaded or owned KRFN when it was active on the App Store.

3. USB Cable

A reliable data transfer cable is required to connect your iOS device to the PC. Avoid cheap charging-only cables.

4. Non-Jailbroken iOS Device

The game client actively detects jailbreaks and will not launch on jailbroken devices. Please ensure your device is running stock iOS.

Preparation: Uninstalling Newer Game Versions

If you currently have the offline version (v3.7.0) installed on your iOS device, you must completely uninstall it before proceeding.

Step-by-Step Instructions

Follow these steps carefully to perform the downgrade installation.

Step 1: Install Legacy iTunes

Download and install iTunes v12.6.5.3, which is the legacy official version that still includes built-in App Store support.

Step 2: Install Fiddler Classic

Download and install the free version of Fiddler Classic (a web debugging proxy tool).

Step 3: Log In and Prepare iTunes

  1. Open the newly installed legacy iTunes and log in with your Apple ID.
    • Note: If you encounter a library conflict error (e.g., iTunes Library.itl was created by a newer version), delete the entire C:\Users\<username>\Music\iTunes folder and restart iTunes.
  2. Go to Account -> Family Purchases (or Purchased depending on configuration) and select the All tab.
  3. Locate KRFN in your purchase history. The icon should have a download cloud mark.
    • IMPORTANT: Do NOT click the download cloud icon yet!

Step 4: Configure Fiddler for HTTPS Decryption

  1. Open Fiddler Classic.
  2. Go to Tools -> Options -> HTTPS tab.
  3. Check the box for Decrypt HTTPS traffic.
  4. You will see several security prompts asking to trust the Fiddler Root Certificate. Click Yes to accept them all.
  5. Restart Fiddler to apply the changes.

Step 5: Intercept the Download Request

  1. In Fiddler, go to the top menu and select Rules -> Automatic Breakpoints -> Before Requests.
  2. Go back to iTunes, and click the cloud download icon next to the KRFN app to start the download.
  3. Fiddler will immediately start intercepting various background requests from iTunes.
  4. Watch the request list in Fiddler. Keep clicking the Run to Completion button (highlighted in green on the right pane) for other requests until you see a request targeting the /buyProduct endpoint.
  5. STOP when the request is paused on /buyProduct.

Step 6: Inject the v3.6.0 Version ID

  1. In Fiddler's right panel, ensure the Inspectors tab is active.
  2. Under the request parameters, locate the appExtVrsId field.
  3. Change the numeric value next to appExtVrsId to the specific ID for version 3.6.0: 
    854995007
  4. Click Run to Completion to forward the modified request to Apple's servers.
  5. iTunes will now download the official v3.6.0 IPA file instead of the latest offline version.
  6. Once the download begins in iTunes, you can disable the Fiddler breakpoint (Rules -> Automatic Breakpoints -> Disabled) and close Fiddler. The cloud icon on the app list will disappear, indicating a successful download.

Step 7: Transfer the IPA to Your iOS Device

  1. Connect your iPhone or iPad to your PC using the USB data cable.
  2. If iTunes prompts you with the error: "This iPhone cannot be used because the required software is not installed", verify that you have cleanly uninstalled all modern Apple software, restart your PC, and try again.
  3. Once the device is recognized, click the device icon in the iTunes top bar.
  4. Select Apps from the left sidebar.
  5. Locate KRFN, click Install, and then click Apply in the bottom-right corner to sync and transfer the app to your device.
  6. If a prompt says "This computer is no longer authorized...", click Authorize and enter your Apple ID credentials to allow the transfer.
  7. Once the sync is complete, KRFN v3.6.0 will be installed and ready on your iOS device! 🎉

Frequently Asked Questions

Q: Why do we have to use this complicated method instead of AltStore?

KRFN features advanced integrity checks and anti-tamper mechanisms (including jailbreak and signature validation). Sideloading via AltStore or other developer certificates invalidates the official DRM signature, causing the app to crash or detect unauthorized signatures upon launch. Downgrading via iTunes downloads a officially-signed IPA matched to your Apple ID, allowing it to run smoothly on stock iOS.

Q: What if I do not have a Japanese Apple ID that previously owned the game?

Since the game was region-locked to Japan and is now completely removed from the App Store, you cannot acquire the game license on a new Apple ID. If you do not have a qualified Apple ID, we highly recommend playing the game on Android or an Android emulator instead.