  Japan is a unique country with a distinct cultural heritage, which is
reflected in billions of historical documents that have been preserved.
However, the change in Japanese writing system in 1900 made these documents
inaccessible for the general public. A major research project has been to make
these historical documents accessible and understandable. An increasing amount
of research has focused on the character recognition task and the location of
characters on image, yet less research has focused on how to predict the
sequential ordering of the characters. This is because sequence in classical
Japanese is very different from modern Japanese. Ordering characters into a
sequence is important for making the document text easily readable and
searchable. Additionally, it is a necessary step for any kind of natural
language processing on the data (e.g. machine translation, language modeling,
and word embeddings). We explore a few approaches to the task of predicting the
sequential ordering of the characters: one using simple hand-crafted rules,
another using hand-crafted rules with adaptive thresholds, and another using a
deep recurrent sequence model trained with teacher forcing. We provide a
quantitative and qualitative comparison of these techniques as well as their
distinct trade-offs. Our best-performing system has an accuracy of 98.65\% and
has a perfect accuracy on 49\% of the books in our dataset, suggesting that the
technique is able to predict the order of the characters well enough for many
tasks.
