|To start, we take Death Blow 3. As mentioned in the Celeritious Cain build, Death Blow is the better option when Cain does not have Cavalry buffs to rely on to buff his Atk and Spd, thus we go for raw damage output on the first two Brave hits rather than trying to go for quads.
For the B-passive, a player can either choose to take Axebreaker 3 or Swordbreaker 3. This is because without Axebreaker, he fails to kill green threats such as Amelia and Hector and requires Axebreaker to finish them off. On the other hand, Swordbreaker allows him to handle Red Sword threats like Ryoma and Ike who can potentially KO him without. Which of the two passives you choose should depend on what your other teammates can cover that Cain cannot.
His C-passive is flexible.The passive he takes here should be dependent on what buffs his teammates require.
We take Luna as our special due to it being a 3-charge skill and its synergy with Brave weapons as well as the 50% Def reduction allowing Cain to take down tanky enemies he normally could not when it procs.
Finally, for his sacred seal, like most Brave builds, more attack never hurts so Attack +1 is the seal of choice.