Time Out says
Azabu Kuroshari spent six years developing its distinctive black sushi. The colour comes from mixing the organic brown rice with edible activated charcoal from coconut shells. It is said to absorb about 90 percent more of the harmful metals found in the most commonly used sushi fish. Moreover, while some sushi uses artificial seasoning and refined white sugar, here those are replaced with fermented plants and organic blue agave syrup, resulting in a lower glycemic index.
There are two seatings per day (5.30pm-8pm, 8.30pm-11pm) and the omakase course costs ¥30,000 per person.
The restaurant also has a membership system with three plans available: the first includes six meals and costs an upfront fee of ¥132,000, the second includes 12 meals for ¥264,000 and the third includes 18 meals for ¥396,000. Those prices may look steep, but buying several meals in advance this way means each omakase dinner works out to ¥22,000 per person.
Note that memberships are strictly limited and new signups may not be available at all times. You can register via Azabu Kuroshari’s Line account.