Ruka -- Trapped in Paradise
ルカ-楽園の囚われ人たち

When I was in fourth grade, I read a book by Ray Bradbury which scarred me for life, and I've avoided reading anything else by him because of that. Something about the feel of this book fundamentally reminds me of that, and makes the book a good deal better than the sum of its parts.
Set in an underground bunker after the apocalypse, the world's last surviving little girl israised by a group of ghosts and her dog. They are watched carefully by the bunker's AI, which has plans of its own...
The plot is obviously cobbled together piecemeal from a dozen really obvious sources. But his ability to play the potentially wacky moe comedy situations -- like the girl watching Roman Holiday and trying to get the ghosts to kiss her -- as searing emotional horror made it easy to forget all that and focus on the book's obvious strengths. I was emotionally invested in the situation almost instantly, and cringed with each new disastrous plot twist.
I read the author's follow up series,
What a Zashiki-warashi Can Do, before I read this -- his debut novel, which won the Grand Prize in the 11th Dengeki Novel Awards. His later series is a blast, a big comedic pop action book that really deserved to earn a bigger following than it did -- and couldn't be more different in feel from this. This guy's the real deal, and I can only hope his new series will finally get people to notice that.
Andrew Cunningham