Starting with SDK Ver.2.99.00, the plugin for smartphone (criware_unity_plugin_smartphone.unitypackage)
include the Android 64-bit version library by default.

When importing a plug-in into Android ARM64 non-compliant Unity, an error occurs during Android build.
If you want to use the plug-in in a non-compliant environment, please delete the following folder.
Assets/Plugins/Android/libs/arm64-v8a

Android 64bit Build Procedure

• Please do the following build setting in Unity Editor:
  Build Settings > Android > Other Settings > Configuration
  
  • Scripting Backend > IL2CPP
    
  • Target Architectures > Check "ARM64"