The answer for this is simple, you can't.
When hair is relaxed the chemical bonds in hair are permanently dissolved. This process cannot be reversed in order to become natural. If you want to go natural you can either transition, big chop or do the stepped chop.
Some hair types don't take very well to relaxer so they never really straighten properly. I have been told by at least one person that because of this when they went natural they didn't have to transition in any way; this was only because the hair never straightened in the first place not because the relaxer process had been reversed.
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