Please refer to the following manual for instructions on how to change the group administrator.
▼Change group administrator (Web Browser)
https://teachme.jp/8/manuals/9030824
There can only be one group administrator per group, and additional administrators cannot be added.
Sub-administrators, who have nearly the same permissions, can be assigned without any limit on the number of people.
▼Assign group sub-administrator (Web Browser)
https://teachme.jp/8/manuals/5009378
Related: If the group administrator goes on leave or resigns and the group administrator role cannot be transferredhttps://help.teachme.jp/hc/en-us/articles/900005509946