Hi Kazuma Yamamoto,
We are very sorry that you are facing the issues with the theme. We checked the theme from our end and it is totally working fine. Sometimes, this type of issue caused because of the plugin conflicts. So, is that possible you can send the login details for FTP or Cpanel from our contact page?
As we know that this information is confidential, but as you are saying you are not able to access the site, we need to check the code directly from the FTP. Or for the quick fix, you can also check once by remaining the theme folder from the cpanel.
Please let us know if you have any queries. We keep your information secure.