Yes, it is possible.
Related：
Invite Users without Email Addresses (Web Browser)
Notes on not registering an email address
- users will not be able to receive E-mail notifications, including emails containing the initial Login information for the Teachme series.
Administrators should communicate the Account name and Password to account users by some means. - If the login password is forgotten, the user will not be able to change or Reset it themselves, and will need to ask an administrator to do so.
- Users will not be able to receive any notification emails from the Teachme series.
- Users cannot become administrators, such as administrators or folder administrators.
If you want to receive notifications without registering an email address
For products that have a notification feature in the mobile app, please consider using "Information on Updates" or "Push Notifications".
However, the information notified from the mobile app is limited.
Reference：[Admin] No-Email User Password Reset (Web Browser)
https://teachme.jp/8/manuals/51167148