4* super merge

Have you fully leveled up your Cain to 40? If not, do so for the special message. Draug already comes with brave sword, but the best unit to inherit brave sword in my opinion is Chrom, who has a higher attack base. I suggest waiting for a Chrom to show up, whether he is 4 or 5 star. Then, I would have him inherit Brave Sword from Draug and Brave Sword+ from Cain. If possible, you could even wait for another Cain with better stats to show up and merge that Cain with the 5 star Cain to get the Brave Sword+.