I received an email invitation from a Microsoft365 group.

When you create a new group or add members to a group on Microsoft365, members of the group may receive the following email.

Subject: You've joined the xxx(group name) group

This email is an invitation message automatically sent by Microsoft365 and is a specification of the service.

Please note that the sender (From) of the email will be the owner of the group (or a random owner if there are multiple owners), but the email is not actually sent from the owner.
If you do not recognize the group to which you were invited, please contact the Information System Division (goiken@sic.shibaura-it.ac.jp), not the sender of the e-mail.