[mgihrrek] Identity by sci-fi drugs

We don't know the mechanisms by which people form and maintain their identity.  Write about a fictional world in which the mechanisms are known -- invent fictional mechanisms for it -- and the characters actively manipulate it.  Maybe they inject specific chosen drugs into children to program specific chosen identities.  Parents and others with power do the injecting.

We then see the result of the fictional manipulation resulting in people with identities familiar in our real world.