The problem wasn't that Lumielle was a loose cannon that might attack to kill Aerin. But she would attack to kill Lyra, that was well within her degrees of tolerance.
The first problem with that was what it meant for her to kill Lyra in the first place. She would certainly leave the Dwarven Bubble, and certainly expose herself. Then she would be putting herself directly in the line of danger on top of that, where the Spirituals would have full rights to kill her if it ever came to that.
But that was only the first problem. What kind of strife would this cause to the Dwarven Race?
Even if Aerin didn't know the extent of Lumielle's true power, he did know how important she was to the Race. Everyone placed both of them on the same level.
If she ended up rampaging because of this, many would take her side. And if she ended up dying because of Aerin's actions, the result would be even worse. It would cause a fissure in the Race that couldn't be solved.
In fact, this might have been part of Flaura's plan as well. If Aerin died after going out to pursue Lyra, the situation would be the same but in reverse.
It was just that Leonel's plan was even more sinister.
If Aerin had been the one to die, the fissure would appear, but it wouldn't be that severe. After all, the main culprit was already dead, so who were they rallying around to be mad at?
However, if Lumielle died, it was a completely different can of worms. In this case, the main culprit-Aerin-would still be alive and well, and presumably still pursuing a relationship with a woman outside of his Race.
This wasn't him realizing that he, too, was in love with Lumielle, or at the very least, it wasn't so obvious to him now. The main problem was that he truly cared for the Pixie, and realizing that he might have unintentionally hurt her hit him like a truck. It was like countless small needles were picking away at his heart.
"I... I need to see her-"
Aerin panicked and began to fidget.
When the old couple saw this, their expressions were even worse. From beginning to end, Aerin didn't blame anyone, not even Leonel who knew of this from the beginning and still went along with this plan anyway.
All he was thinking about was the role he played in it all and how he could have acted to make sure it didn't happen.
He took it all on his shoulders like he usually did. In fact, even if it meant ignoring his love for Lyra, so long as he could make Lumielle feel better, he would marry her right now.
Although he had fallen for Lyra, how could that compare to someone he had known his whole life? If he had to make a decision, there was only one to make.
Just like he had chosen to cut Lyra off the first time, he could do it again.
Leonel's hand suddenly firmed up. "Relax for a bit," he chuckled, "the end of the world hasn't come just yet. If my information is correct, the odds that she's seen the Dream Pavilion battle is close to none, correct?"
He looked toward the old couple who seemed even more shaken now. Just how much did Ryu know, exactly?
"If we're going to do this, then we need to do this right. If you all listen to me, we'll come out on top and make a certain someone pay dearly."