Hello @馬場 勇真 !
As we can read from https://learn.microsoft.com/en-us/entra/identity/hybrid/whatis-hybrid-identity
Hybrid identity is accomplished through provisioning and synchronization. Provisioning is the process of creating an object based on certain conditions, keeping the object up to date and deleting the object when conditions are no longer met. Synchronization is responsible for making sure identity information for your on-premises users and groups is matching the cloud
So as long as your user is syncing from On Premises AD to Entra ID it is a Hybrid Identity user.
I hope this helps!
Kindly mark the answer as Accepted and Upvote in case it helped!