It wasn't in Fubuki's plans but it was meant to be. At the point where they meet at the different sides of the altar they are in direct opposition morally as well. For FBK this has been just a fling that took a bad turn and ruined her heart, but for Kanata every day was spent struggling for family's happiness, and that's both completely out of sight of one another. For FBK at that point happiness didn't matter while for Kanata it was what mattered the most. Couple this with the fact that Kanata wanted to believe Fox is a good guy after all, and that Kanata was the person least likely to pull the trigger with such conviction and prejudice under any other circumstances, I dare say there was nobody else who should've taken that shot.
