Black rust near edge - Henkotsu Kamisori. Advice?

I think it's Henkotsu "Hinoshita Kaizan"
https://photos.app.goo.gl/oLqUT5S9AWLoLWeFA

Any advice? W/D paper? Metal polishing compound..?

Man that sucks. Let's hope that doesn't go all the way through. I would try some 3M Marine metal polish first, maybe on some steel wool.

May as well shorten it up. Getting through that will have you a toothpick?

Sadly, with a closer look at those photos I'm afraid you will never get to good steel on that edge looking at pic #2 and pic #4 it looks like it is in fact all the way through in that one spot where you can see it on the back side. I think I might try some Polish just to see if it is just at the surface there but I'm afraid you'll find it goes deeper. I have had blades that had very minor looking spots that would just keep on chipping at the edge as you hone. That rust gets down below the surface and works it's way through the whole blade. As you hone it just reappears at the apex. Sometimes you can find a sweet spot where there are pockets just up from the apex and you're good for a time (kinda like Wyatt Earp dancing between the bullets)but one more hone and it's chip city. Sucks too because that one looks like brand new otherwise.

Might clean it up cosmetically and make a display piece out of it.