Assigned to protect a royal procession transporting a powerful artifact called the "Ouin," Squad 10 gathers in the human world as Captain Toushirou Hitsugaya and Lieutenant Rangiku Matsumoto observe the area cautiously. However, the caravan is suddenly struck by a group of assailants who wreak havoc on the procession, stealing the Ouin in the process. After a brief clash with one of the attackers, the distraught Hitsugaya pursues the escaping thieves, leaving behind Matsumoto and the disoriented squad. Following the incident, the Seireitei brands Hitsugaya a traitor for abandoning his post and puts Squad 10 on indefinite lockdown.

In the human world, Ichigo Kurosaki is investigating a spiritual abnormality when he stumbles across the injured Captain, but is caught off guard when Hitsugaya suddenly flees. Soon learning of the situation, Ichigo, Rukia Kuchiki, Renji Abarai, and Matsumoto set off to prove Hitsugaya's innocence and uncover the truth behind the theft of the Ouin. Meanwhile, a ghost from Hitsugaya's past haunts his thoughts as he chases down the true culprit.

[Written by MAL Rewrite]

Special episode bundled with the 9th volume of the manga based on Chapter 57-59.

Extra short anime "Ura-On!!" included in the limited edition of the K-ON!! Blu-ray.

Ever since her late mother took her to an aquarium when she was young, Tsukimi Kurashita has been obsessed with jellyfish, comparing their flowing tentacles to a princess's white dress. Now living with five other unemployed otaku women, 19-year-old Tsukimi spends her days as a social outcast dreaming of becoming an illustrator. However, her life changes forever when one day, a beautiful woman unexpectedly helps her save a jellyfish in a local pet store. From then on, the stranger—confident, fashionable, and the complete opposite of Tsukimi and her roommates—begins to regularly visit the girls' building. This trendy hipster, though appearing shallow at first, harbors some secrets of her own, starting with the fact that "she" isn't really a girl at all, but a wealthy male college student named Kuranosuke Koibuchi! [Written by MAL Rewrite]