The second stage of the battle royale known as the Sekirei Plan is underway. Shintou Teito has been closed off; no Sekirei or Ashikabi may leave. Minato Sahashi and his harem of Sekirei must now prepare to fight new battles as changes to the rules are put into place. However, not all groups will return to the battle: some Sekirei are loved very much by their Ashikabi partners, who would rather forfeit the prize than see them perish. In the midst of the action, someone close to Minato may be more involved than he had ever imagined, and threats lurk around every corner. There are even rumors that the "Single Numbers," the most powerful type of Sekirei, have entered the fray. In the eyes of the "Game Master" Minaka Hiroto, everything is proceeding according to plan. [Written by MAL Rewrite]

"Kusano's first errand" - A ten minute OVA that came along with the 6th vol. limited edition of Sekirei. Kusano finally tires of nobody admitting her as Sahashi's potential wife, so she insists on joining Musubi and Tsukiumi on their shopping race to show her abilities. An iffy day ensues.

Episode 0, consisting of two subepisodes: "Sekirei Shindan" (鶺鴒診断) and "Sekirei Yoka" (鶺鴒余暇), of Sekirei: Pure Engagement included on the first DVD/BD volume.

Six months ago, Lord Hugh Anthony Disward, also known as Huey, lost his eccentric grandfather, Sir Wesley Disward, who was a renowned collector of rare books. His grandfather's will states that, in order to inherit his manor and everything inside it, he must take guardianship over the Bibliotheca Mystica de Dantalian—an archive that contains forbidden knowledge—and also take care of a mysterious girl called Dalian. As Huey settles into the manor, an old rival of his grandfather's arranges a meeting with him. Dalian, knowing the rival to be Wesley's killer, tags along and discovers that the murderer is in possession of a Phantom Book—a cursed tome that Wesley tried to seal away. When the book puts the two in danger, Huey discovers that the Bibliotheca Mystica de Dantalian and Dalian are one and the same, and she entrusts Huey with the key to unlocking the knowledge stored within her. Together, Dalian and Huey seal the book away, and thus begins an unlikely partnership as they solve mysteries caused by other Phantom Books. [Written by MAL Rewrite]