In Magipro, Ruler is what Mokuou Sanae can’t be in the real world: in control. She always ranked at the top of her class, but speaking out of turn at the office where she worked got her reassigned by a boss who wanted her to learn her place. She always saw everybody in the world as idiots to be brought to heel. It’s how she ruled as Ruler, and it was her downfall.
Getting Ruler’s backstory was a sure sign that she’d be the next victim, despite having come up with a devious scheme to steal Snow White’s Magical Candies. As it happens, her desire to keep distance from her subjects by insulting them at every opportunity became her fatal flaw when she relied on Swim Swim to transfer Snow White’s candies while she held her pose to keep Koyuki from moving (the flipside of her magical power to control).
As such, Swim Swim took it upon herself to doublecross Ruler, only taking half of Snow White’s 50,000+ candies and distributing them evenly to all but Snow White herself, La Pucelle…and Ruler. That puts Ruler in last place at the time of the rankings, and it kills her.
Tama seems torn up by the coup, but the twin “angels” are fine with it, and acknowledge Swim Swim as their new leader. In a nice twist, Swim Swim was the young girl who Nemurin said could be a princess if she tried hard enough. But Swim Swim couldn’t be the true Ruler until the old one was eliminated. And so it comes to be.
The entire situation disgusts Koyuki, who was ready to die rather than let anyone else die in her place before she learned Swim Swim only took half of her candies. But Souta isn’t so dedicated to Koyuki’s ideals, especially if it means Koyuki’s death. So La Pucelle re-vows to be Snow White’s knight, doing whatever is necessary to keep her alive and safe – whether Snow White wants such treatment or not.
With the sixteenth magical girl entering the field, Koyuki will no doubt continue to need protection, not just from those who would eliminate her, but from her own stubborn refusal to defend herself at the cost of others.
RABUJOI - An Anime Blog 
The emerging formula of telling the backstory of a character that will die in the same episode is similar to that of Bokurano. However, the problem with MagiPro at the moment is that all the characters who have died so far are not really that sympathetic. Nemurin is a lazy slob and Ruler is a haughty woman. And their backstories, at least in the anime, do not even bother trying to establish at least some aspects where we can care for them. So, for the show to really drive in the true weight of the magical girl game’s rules, they need to estavbish another sympathetic character aside from La Pucelle and Snow White.
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I would have to disagree that the deaths have no weight. They do have weight – on the protagonist, Snow White because it completely violates her expectations of the game, and also because her incredible success will doom someone inevitably. So the weight of the rules depends on how much you sympathize with Snow White, and how much the impact the rules of the game has made on Snow White psyche you choose to sympathize with.
That being said, Mahou Ikusei is displaying very tight and coherent plotting. Ruler’s death was set up by the butterflies launched by the final moments of Nemurin’s life. And that puts it above failed “Dark magical girl shows” such as Daybreak Illusion that were held back by very incoherent plotting and often shallow character archtypes.
I still suspect though, that La Pucelle is a dead man walking.
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