The copywriting comes from Weibo:
The immortal witches are invulnerable to fire and water, but love can kill them. Once they are loved, their lifespan will end. The deeper they are loved, the shorter their lifespan will be.
So there was a tradition that when witches became bored and no longer wanted to live, they would pick up a child to raise.
They even have a textbook manual to teach you how to be a good parent so that your adopted son will rely on you, admire you, and love you.
Manual title "Suicide Guide"
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Concept: Love has two sides