The name of this ship was just so badass-sounding and ridiculous, I couldn't help but write a fic for it. Whoever came up with the name "MurderPrincessShipping", I could kiss you. But I can't over the Internet, so have a short fic about the pairing you named. Too bad the title of this fic isn't as awesome…
Disclaimer: Blu doesn't own the Pokémon series. Only this fic.
Summary: He would see the world die before she would.
X-X-X
She was the only human companion he had—the only companion he had period. None would dare to come close to the infamous Yveltal, a creature whose life was only sustained by taking others'. So to have a human wish to save him, and then want him around, was odd. But over time, he grew to enjoy the human girl's company. She treated him with such love and care, it was a completely new and refreshing experience. It made his heart feel light when she would stroke him and feed him with a smile on her face. Suddenly, bonds and love didn't seem to be such fragile, pointless things.
And yet, she was still as vulnerable as any human. Still capable of dying from causes both natural and unnatural. Even Yveltal itself was a risk to her life, the moment he needed to elongate his lifespan and absorb the life from. It saddened him to think that he might cause her death one day. It saddened him to think that she had to die at all.
So he when she strokes her in such a way that he can't help but envelop her in one of his wings, he thinks that this will be how it will end. If he has to find a way to ensure that she would live for as long as he would, he would find one. If it came down to stealing the life of others to ensure that he would forever be with her, he may well do so—for them. Because Yveltal would see the world and every creature on its surface die before she would.