A cloud-based identity and access management service for securing user authentication and resource access
If you have access to 2 different tenants that means your account is provisioned in both the tenants.
Now, if you want to remove your account from one of the tenants, then Global admin of tenant can remove your account. Or you can also leave the directory.
When it comes to leaving your second "Default Directory", you should be able to do this through the Azure Portal or your My Account page. For more info - Leave an organization as an external user.
Note: You can usually leave an organization on your own without having to contact an administrator. However, in some cases this option won't be available and you'll need to contact your tenant admin, who can delete your account in the external organization.
Azure Portal:
Within the Azure Portal navigate to your Azure Active Directory
Select Manage Tenants
Select the Tenant you want to leave and select Leave tenant

My Account page - How to leave an organization
To view the organizations you belong to, first open your My Account page. You either have a work or school account created by an organization or a personal account such as for Xbox, Hotmail, or Outlook.com.
If you're using a work or school account, go to https://myaccount.microsoft.com and sign in.
If you're using a personal account or email one-time passcode, you'll need to use a My Account URL that includes your tenant name or tenant ID, for example: https://myaccount.microsoft.com?tenantId=wingtiptoys.onmicrosoft.com or https://myaccount.microsoft.com?tenantId=ab123456-cd12-ef12-gh12-ijk123456789.
Select Organizations from the left navigation pane or select the Manage organizations link from the Organizations block.
Under Other organizations you collaborate with (or Organizations if you don't have a home organization), find the organization that you want to leave, and then select Leave.

Note: In the Home organization section, there's no link to Leave your organization. Only an administrator can remove your account from your home organization.
Additional Links:
Manage organizations for a work or school account in the My Account portal
Why can’t I leave an organization?
Let me know if you have any further questions.
Please "Accept the answer" if the information helped you. This will help us and others in the community as well.