Images are captured from the Shiin (Death Mark) manga.
There are some differences between game and novels, and I recommend you to read them.

Information about books:
『死印』 (小説)
雨宮ひとみ / エクスペリエンス
『死印』 1巻 / 2巻 (漫画)
恵那 / エクスペリエンス

There is one more book about Spirit Hunter: NG :
『NG』 (小説)
エクスペリエンス / 黒史郎

All of them can be found in some online shops.
E-book or paperback version are available.