Sadaharu: P.S. there's no need for one more move from the defender because the next move is to take the ko. If the defender plays any more moves it will be a waste of ko threats.
d4rkm4tter: So E19 by the opponent would be a mistake, they should take the ko? Ok, I reverted it back.
Sadaharu: @d4rkm4tter your solution is not ko anymore because black can play at E19 to kill after white takes at B19. I think it's better to leave the problem as it is. White has to fight that ko in the original solution .
So E19 by the opponent would be a mistake, they should take the ko? Ok, I reverted it back.