Depending on your patience you should reroll for a black.
At 3% and average luck it takes only 17 rolls to get one, considering you get 3 rolls per account (2 from crystals and one from fame wich I can confirm give blacks as i had 2:Lapis and Toma from it in 2 diff accounts), still on average luck it would only take you around 6 accounts to see a black.. you can use the same mail by deleting account with https://www.dmm.co.jp/my/-/inactivate/