For those who don't know, the series Touka Gettan crosses over with Yami to Boushi to Hon no Tabibito with the appearance of Hazuki, Lillith, Ken-chan and Hatsumi/Eve from the older show. As both series (and games they were based on) are from the same studios (in the animes' case, Studio Deen), this should not come as a surprise. Series crossing over with others has become somewhat all the rage of late....
Essentially, episode 14 is like an extra episode of YamiBou, with the travellers searching for Hatsumi in the world/book of Touka Gettan. A lot of it doesn't make much sense, but then YamiBou tried to play with ppls minds by leaping around more often than The Melancholy of Haruhi Suzumiya. Touka Gettan pretty much does the same thing, only more incoherently. And it is full of the fanservice we've come to expect from both series.