@Koutarou Shimozono Greetings!
To change the name that appears when you receive an email about an invoice from Microsoft, you can update the contact information associated with your Microsoft account. For more information see this link - https://learn.microsoft.com/en-us/azure/cost-management-billing/manage/change-azure-account-profile#change-your-contact-email-address
Note: Once you have updated your contact information, the new name should appear on any future emails you receive about invoices from Microsoft. Please note that it may take some time for the changes to take effect.
If there are any challenges or you need any further assistance in this matter, you can reach out to Azure billing and subscription management support by raising a support request. The ticket enables you to work closely with the support engineers and get a quick resolution to your issue.
Here is the link - https://docs.microsoft.com/en-us/azure/azure-portal/supportability/how-to-create-azure-support-request to create support case.
FYI: Azure Billing and Subscription Management support is included in the Basic Support Plan without any charge.
https://azure.microsoft.com/en-us/support/plans/
Hope this helps!
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