Group ID, group display name, account name and password have the following character restrictions.
•Group ID
[Available characters] Numbers 0-9, uppercase letters A-Z, lowercase letters a-z, symbols "._-"
[Character count] 1 to 40 characters
[Other] Group IDs already in use cannot be used.
Spaces cannot be used.
•Group Display Name
[Available characters] Numbers 0-9, uppercase letters A-Z, lowercase letters a-z, kanji, hiragana, katakana, symbols
[Character count] 1 to 50 characters
[Other] Single-byte and double-byte characters can be used for the following.
Alphanumeric characters, katakana, symbols.
•Account Name
[Available characters] Numbers 0-9, uppercase letters A-Z, lowercase letters a-z, symbols "._-"
[Character count] 1 to 50 characters.
•Password
[Available characters] Numbers 0-9, uppercase letters A-Z, lowercase letters a-z, symbols
[Character count] 8 to 64 characters
[Other] Cannot be the same as account name, password strength "Intermediate" or higher.
Related:
What symbols can be used for passwords in Teachme Biz?