You are a Magical Girl, your soul is in a Soul Gem that gives you magic. You can survive lethal wounds, but if the gem is shattered or corrupted, you die. Using magic or experiencing negative emotions darkens your Soul Gem with curses. But if it turns completely you will become a Witch, a being of despair. Your Soul Gem has a range of 100 meters from your body. You can also control your pain by adjusting the connection between your Soul Gem and body. Powers that protect your body also protect your Soul Gem.
You have the opportunity to make one wish. Your wish determines your unique magic, weapon, and strength based on your karmic weight and potential to change the world. Your karma can increase even in a time loop, merging fates with alternate timelines and increasing your karma. Your karmic weight also depends on how much SP you spent on powers and upgrades. The total karma you possess is 1/5th the amount of SP spent. If you have more than 150 Karma, you can rewrite everything in reality across time and space in the multiverse and become the Ultimate Magical Girl.
You can still grow stronger after creating your wish by learning creative ways to use your magic, enhancing your soul, or being an important individual that influences the fates of others. Unlike other magical girls, you will not lose karmic weight and magic as you grow older. You can create Grief Seeds to purify your Soul Gem from corruption, but it consumes energy and can darken it with curses. You need to balance creating and using Grief Seeds to avoid becoming a Witch.
(You can wish Endbringers or even Scion away based on the cost of End of the Kaiju or Overcharge Strike.)