Perfet place for taking nap
Comic cafes (or Manga Cafe) are perfect place for taking nap. You fill out a registration form at a counter for the first time then you will be assigned a chair or flat mat. Those spaces are separately by walls and are usually equipped with a desktop PC with a headset.
You might want just browse internet, send/ receive emails on web-based services, work on documents you brought by USB memory stick and read manga, magazine, newspaper (mostly Japanese). There are snacks, instant noodles and beverages for sales.
Manga cafe is a perfect place for taking nap in secure and quiet environment (little smoky though).