Try 7 days at 10 sorties a day, minimum. Just for the Last Dance. My bucket count hit rock bottom twice just trying to sink BB Water Oni for the last time.
See, that's why you leave the Boss killing to other torpedo shipgirls, like Shigure and Yuudachi. (My Yukikaze wasn't properly leveled for this event.)
I learned from a stream that Kitakami's luck is too low for torpedo cut-in, and equipping her with 2 yellow guns is much better. She hits just as hard and the damage is much more reliable.
