Hyouka - Season 1 Episode 15 -

The Classics Club come up with the idea to catch the "Juumonji" thief by using Houtarou's skills. Doing so will advertise the Classics Club even further. Houtarou quickly figures out that the clubs affected by the thefts have been in alphabetical order (according to Japanese hiragana alphabet). They also suspect that the items stolen also follow an alphabetical order. Finally, Houtarou tells the group to stop reading Juumonji as a name; doing so reveals that Juumonji actually stands for "ten letters". Following this order reveals that the Classics Club will be targeted next.