If you have issues with the engine, make sure you're using the latest available version. You can update the package using Unity Asset Store interface: Window -> Asset Store.
If updating didn't help, try to re-install the package by deleting Naninovel folder from the project and re-importing it from the Asset Store. Be aware that by deleting the package folder you'll lose all the engine configuration data; you can keep the configuration by migrating Naninovel/Resources/Naninovel/Configuration folder to the new package installation folder.
Always remember to backup your project (or use a VCS) before updating or deleting a package. Haruhi God knows what could happen in the process.
In case the above steps didn't help to resolve the issue, check the issue tracker — chances are the problem is already being worked on. You can also create new issues there to ask a question or report a bug. When reporting a bug, please use bug template and fill in the required information.
Not comfortable using GitHub? Check out Unity forum thread. To discuss the issue in private, send a private message.
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