Narnia is doing this at Baal's request. Firstly, he made sure that she was going to be in a life-threatening situation while close enough to Iruma to be healed. Second, it extracts Shiida, who has been away on the mission for far too long and was starting to lose sight of the mission. Thirdly...
Bro is using all that mana for a technique and he just punches with it. I know they don't mention it, but that's probably the least efficient way to use all of that mana.