The World is Made Out of Closed Rooms

世界は密室でできている

• by Maijo Otaro
• published by Kodansha]

A bit harder to describe - the narrator's best friend, Runbaba, is a minor character from Smoke, Soil, or Sacrifices, and this book traces the two boys' adolescence, from Runbaba's sister's suicide through a series of closed room mysteries. But it's also a very funny coming of age story, as the narrator runs into two crazy sisters, both older than him, and the chaos they bring with them.