You use the standard procedure for removing extensions from Business Central. See Install and Uninstall Apps - Business Central.
When you uninstall the Yokoy connector, the system removes all extension-related objects. By default, data is retained unless you want to explicitly delete it by selecting the Delete Extension Data option during the uninstallation process. This means that if you choose to reinstall the extension, any retained data can be used by the Yokoy connector unless you chose to explicitly delete the extension data.
You may find that the Yokoy connector has been uninstalled automatically after a Business Central update. Since data is automatically retained, you just need to reinstall the extension to resume working with the Yokoy connector.