This is like the hero vs villain thing. Sacrifice yourself or the one you love to save the world… or sacrifice the rest of the world to save the one you love. Now, wouldn’t it be interesting if the two of them were lovers/family? ?
My fictional premise will inherently lead to the climax of this scenario even the climax of volume 2 leads to this... and yes, they are a family that loves each other.
Someone is clearly planning a genocide. Nice knowing ya Envy.
The story I have done, Azure Night. Has a similar premise. Where the protagonist chose to become the enemy to save their partner from being sacrificed for the ‘Greater Good’.
I put that in quotes, because apparently it was widespread oppression and or death.
Every path demanded the other’s death, and the protagonist kept giving up more. Until the last thing they can gamble is their existence, so they gambled it on the tiniest chance for success.