If you have a Sub-administrator account, you can change the Administrator through the Sub-administrator's proxy operation.
Since a Sub-administrator cannot change their own privileges to "Administrator," you will need to temporarily log into the old Administrator's account to make the change.
For the procedure, please refer to the applicable manual.
▼Change Administrator via Sub-administrator (Web)
https://teachme.jp/8/manuals/51166988
If you have not set up a Sub-administrator, or if there are no longer any users set as a Sub-administrator, please contact support@teachme.jp with your Teachme series Group number.
▼How to Check Your Group Number
https://teachme.jp/8/manuals/51167005