NEW Joukyuu Wide & Large 142 g (and getting more and more rare to mine) Asano Mikawa Nagura Koma Slurry Stone

Not some Vintage Koma that has been sitting around for 20-30+ years and trade by multiple users, newly ranked (found what's still existing from the Nagura mined) by Asano Family.

Wide and Big enough to use as a hand whetstone and a travel koppa

The last slurry stone in an authentic JNAT Nagura Progression, many found that if you use the Koma before Water x the Finishing Stone, the edge would be much sharper but comfortable. However, I found that Koma for refreshing an edge sometimes gives you an edge better than the original hone, but that's my opinion.

Not to mention for a truly beautiful bevel or a beautiful snow "kasumi", Koma is needed to get the real fine scratches left by the previous nagura progression or even a pre-finish synthetic stone.

You want to get a Large size for a Koma as you'll be using this nagura level more (compared to level like the Ban) since you'll also use it for knife and razor refreshes along with honing from scratch. If I were to refresh a dulling edge, I would start with a Koma Slurry to Finishing on a Finisher Stone with a Tomo-nagura or just water.