Megumin's Growth Stone Sequence (Patreon)

Megumin picked up a crystal from Wiz's shop—an "expansion stone" that was supposed to double the size of its target. She thought it would be a good idea to use it on herself, but Wiz failed to warn her that the effect works differently on humans: while it merely doubled the size of objects, on a human it caused a fivefold increase! Megumin discovered this too late; at first, she was fascinated by her growing breasts, but her joy vanished when they—and subsequently the rest of her body—expanded massively. Her clothes tore, leaving her naked in the room, until she grew so large she burst right out of the house, shattering the roof and walls with her enormous breasts and feet. Now she is somewhat embarrassed by what happened, and she hopes the change isn't permanent.