Hi @masahito,
Do you want to add other custom column values within your SharePoint library into your email body?
Do you use the "Send an email when a new item is created in SharePoint" built-in template to create your flow? Do you customize your flow based on this built-in template?
You could not set value for these column columns within your SharePoint library when the file is uploading to your library, you could only set value for these custom columns after the new file is uploaded to your SharePoint library. In addition, I think there is something wrong with the trigger that you used within your flow.
I have created a SharePoint library on my side and the data structure of it as below:
I have made a test on my side and please take a try with the following workaround:
- Add a "When a file is created or modified (properties only)" trigger, specify Site Address and Library Name.
- Add a Condition, click "Edit in advanced mode", type the following formula:
@equals(triggerBody()?['Created'], triggerBody()?['Modified'])
- Within "If/no" branch of Condition, add a "Send an email" action.
Image reference:
The flow works successfully as below:

Note: The email would be triggered when you set value for these custom columns (properties) within your SharePoint library.
Best regards,
Kris