First I would steel it to see if any was just rolled. Next step, I know nothing other than removing material to get back to the burr. It doesn’t look like that much will be needed to me from your pics. Should be much easier if it’s already seen the wicked edge once and the settings were recorded. If it were me personally, I would back down to 600 to try removing material (depends on the steel, of which I know knotting about Hitachi Aogami) and, see if 400 was needed, and then work my way up normally.
Enjoy the great knife I say, after all they are tools meant to be used foremost. A few knicks and chips along the way are just badges of pride.