When people discovered that finite girls had the power to fight against demons, they enshrined them as gods and respected them as gods.
But in fact, they are caged birds that are unable to spread their wings, tightly bound by chains of prayers and wishes!
Their world is only fight, and then death...
Getting married and having children will weaken their abilities and are taboos that are not allowed.
Love has no effect other than causing tragedy. Don't try, don't get emotional...
Then, when the power is exhausted, the fire of life is extinguished...