Franka.

Franka used "invisibility" to follow Lumian all the way here, and the first target she chose was the "Short Candlestick" Castina who could provide protection for "Black Scorpion" Roger.

She didn't directly assassinate "Black Scorpion" Roger, because she was worried that the fatal blow that could threaten the opponent's life would cause the "magic circle" with double effect to automatically activate. The Hidden Blade that was burning with black flames popped out, and with Franka's full blow, pierced into Castina's back with a poof, piercing through her heart.