NOTE: please use the "Bug reports" thread for reporting any issues you encounter.

If the game launches with a bluescreen error message (possibly with lots of ???s), please try the following two potential fixes. If neither fix works, please contact FAKKU support at the following link:
https://www.fakku.net/contact

Method 1:

1. Open Windows Control Panel
2. Select Region
3. In Region settings, select the Administrative tab
4. Click Change system locale
5. If enabled, uncheck the "Beta: Use Unicode UTF-8 for worldwide language support" option
6. If this doesn't work, try changing your current system locale to Japanese

Method 2:

1. Ensure that your antivirus software is not blocking the game from running if you use one
2. In addition, open Iku Iku Succubus's install folder
3. Right click ikuikusuccubus.exe and select Run as Administrator