d-account is customer ID for d-point, d-market and so on.
The name is changed from "docomo ID" on 01/12/2015.
※You can still use docomo ID instead of d-account.
※Everyone is able to create d-account. To create d-account.
※You can check the steps for creating d-account.
※For more infomation, please got to d-account page.