The Witch At The End Of The World summary:

1000 years ago, a war between humans and space witches ravaged the stars, destroying countless planets and taking even more lives. Eventually, the humans captured the most powerful witch and imprisoned her as a war criminal under the treaty. The castle where the Magic Lord is sealed away is watched over by a village where everyone has developed weak magical powers- everyone but Mugi that is. Determined to prove that he doesn't need magic, Mugi accidentally flies into the monster-infested forest surrounding the castle and is saved by a girl that he has never seen before...