Care of Japanese Hocho Knives

When I lived in Japan many years ago, I happned to aquire several Japanese hocho knives. These are the ones with the very fine steel which are beveled on just one edge, and have a handle of boxwood I believe.
I love and treasure these knives and have done my best to keep them sharp and clean, I use them every day.
Over the years dispite my cleaning and polishing, they have become somewhat dull and have develped dark stains I have used fine sandpaper on them that helps [ probably a no-no] but not to satisfaction.
I would like some help in really cleaning them to the extent possible. Sending them away is not an option.
Any ideas. ?
The knives are over 40 years old and have held up beautifully. I have choppers, sushi, general purpose knives and others, about 10 in all. Thanks.

The sandpaper isn't used as you say, I think. Polish kitchen knife at the grindstone is best. After a Japanese Meiji government,19 century Samurai no longer carry swords. Japanese sword smith made a great kitchen knives.

https://books.google.co.jp/books?id=WwlFDQAAQBAJ&pg=PA3&lpg=PA3&dq=jap...

Cheers

One more this is English link.

http://www.sakaiwada.com/english

Thank you Kaoru san

I looked at the two links and read them carefully. I did find a little advise that I will consider, but I am not sure I want to use a grinding wheel unless it has the proper stone or buff polish on it.
Alternatively they say to ship them to Osaka. That is not an option as I would not want them to get lost in the mail. Maybe I could try one and see how it goes.
I do now understand that I need to sharpen them more aggressively. I have been to easy on them.
While I love these knives, because of the very high quality steel they start to rust immediately after use. This is usually not a problem but over the years the stains build up.

On second thought...perhaps Osaka is nice this time of year...haha

You can do it by myself like this.
https://youtu.be/dfW0VwJVHI0
https://youtu.be/AYGFxjiGnqw

What is "まくれ makure"?
http://oisiso.com/houtyou.html
http://siso-lab.net/wp-content/uploads/2012/06/1339725015.jpg

In Japanese households we commonly use the 砥石 (to-ishi: whetstone) shown more clearly in the videos that Nalice provided. And then once in a while, some people might have their knives professionally sharpened.

If you ever come to Japan again, or if you have a Japanese community in your area, you can bring along your knives to have them sharpened by a professional 包丁研ぎ (houchou-togi).

Thank you both for the helpfull insights.
I have several wetstones which work well but the stains I am referring to are on the flat of the blade. I think the video was most helpful but my Japanese is almost non-existant, but I got a lot from it anyway.
Uco...I expect that you have long since got rid of that plastic flower...yeah..I remember. Hope you are well.

If you're talking about the plastic azalea I picked up at Honmoku, I'm still looking at it.

As for your stain, it seems that you don't have to worry about certain stains. Why not have a Japanese restaurant owner take a look at it? The link about hocho stains is just for your reference.
http://www.suisin.co.jp/toku02/2011-03/index.htm

Uco san

You still have those plastic flowers...? I would have thought they would have been lone gone..good for you..they must have some fond memory attached to it.

While I am not worried about the Hocho blade stains, I sure would like them to be the best they can be. Unfortunately there is no Japanese community in New Hampshire [that I know of] so there is no one to consult with. I have found a guy with a grinding wheel and buffer. I will try that.
I see the new ones for sale and sure would want them to look like new.

There was a store on Isezaki-cho [Yokohama]that sold all kinds of Hocho's and had a display that I still remember. Covering one whole wall there were very small ones to outragiously oversize ones all lined up by size..I was impressed. As I could afford, I bought many of them there. The shopkeeper spoke very good english and we got to be what I would like to say, friends.

I also remember seeing a street food vendor using one, he wiped it every 5 seconds, it looked very beat up, I almost offered to but it from him but it was too awkyark ..and a little creepy. So I didn't.
Thank you all for your help.
Peter