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Well, I did this tutorial since many people have problems in this.
All the models contain bones, all the bones of the models have the same names, there will NEVER be a model with different names to other models, since this can cause errors; (The model would not work when opening MMD, poses, motions, etc.)
When the hair bone does not follow the head, it is because the hair bone does NOT have the same bone name as the head.
Therefore, the central bone of the hair must have the name of the head (頭).
Do not edit the name of the bone while it is put on the model, open the hair only in a new Pmx.
Name of the head bone: 頭