Yuri's Guardian (Kyo Kara Maoh Fan Fic)

Miwa Aragaki was a normal high school student. She practices martial arts with her older brother, mainly because she has no choice. One day, she was showering and is suddenly sucked into a world that needs her help. She must save the demon king, Yuri Shibuya. When she saves him the first time, Conrad makes her his official guardian for when they are in need of it.
Miwa's life became a lot more exciting, and she enjoys it. She feels like she's a part of something, now, and that is all she really wanted. Now, she juggles the job of being the guardian of a king in another world, and school.