Error book
The cards you answered Again in Today, grouped by test section and level, with the ones you miss most first.
Your error book is empty
Cards you answer Again in Today land here, grouped by section and level. Your book is read from this browser once the page has loaded.
The book is read from your progress in this browser on this device; nothing is sent anywhere. Misses in the kana drill and the placement check are not collected here: the drill brings a missed kana back by itself.