When the end of the world comes, your first reaction should be to rush into the kitchen to get a kitchen knife, or pick up a sharp weapon at hand.
Raise your hand and hold the weapon tightly, and calmly chop off the head of the "human" coming towards you.
Congratulations on never being a normal person again.
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The heroine is an ordinary person, short story, in the first chapter the heroine has entered an invincible state
There are superpowers, various cheats, time travel, and rebirth.