Saigami

Saigami summary:

Hanasaki Ayumi can't quite find her place in the world with every day being one of emptiness and loneliness. But on the day she receives a mysterious letter, everything changes. Finding herself in a frightening new world full of unexpected adventures and fanciful characters, she joins in the journey of two adventure-seeking young men. Hoping that she'll find a way home, Ayumi soon realizes that the more time she spends in this strange, new world, the more she gets tangled up within it and the greatest questions of all: Who is she? and Where does she belong?