I'm a librarian who loves anime, manga, and reading a wide variety of genres.
The ending: marriage counseling for deities.
"'It's over, it's over! No more Darkness, no more Light. No more friends or foes. There's nothing left to do. How about a snowball fight?'"
I'm not sure how I feel about this book. Parts of it were amazing, parts of it were mediocre, and I disliked the way Saya felt like a secondary character disguised as a main character for most of the book. Maybe 3.5 stars? I definitely plan on getting the second book, which is thankfully still in print and reasonably priced.
As far as the game goes, I read this for the "Arsenical Toothpaste" card. Noriko Ogiwara is a woman, and her given name starts with one of the letters in the word "arsenic." You could also argue that Lady Iwa, who was so old that no one knew her real age, was an important character, since she made the ending possible.