In the dry riverbed of Arakawa River, undefeated elite Ichinomiya Kou (aka Ric) met the lovely homeless girl Nino, a self-declared Venusian. Their awkward love stirs up trouble among the other strange inhabitants of the riverbed. (Source: ANN)

Owing to an increasing debt, Kaiji Itou ends up resuming his old lifestyle. One day, while walking on the street, he stumbles upon Yuuji Endou, who is hunting Kaiji due to the money he owes to the Teiai Group. Unaware of this, Kaiji eagerly follows Endou, hoping for a chance to participate in another gamble, but soon finds out the loan shark's real intentions when he is kidnapped. Given that Kaiji is unable to pay off his huge debt, the Teiai Group instead sends him to work in an underground labor camp. He is told that he will have to live in this hell for 15 years, alongside other debtors, until he can earn his freedom. His only hope to put an early end to this nightmare is by saving enough money to be able to go back to the surface for a single day. Once he is there, he plans to obtain the remaining money needed to settle his account by making a high-stakes wager. However, as many temptations threaten his scarce income, Kaiji may have to resort to gambling sooner than he had expected. [Written by MAL Rewrite]

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.

The story revolves around Maya, the daughter of the former Headmaster of Waldstein Academy, and a time traveling agent Fumiaki Uchida. In the year 2012, the world had been invaded by aliens and time travelers were sent back to the year 1999 in order to find and destroy the Nostradamus Key, which Nostradamus Prophecy foretold as what would bring about the apocalypse. The series then turns to the year 1999, where Maya returns to the Academy with the intention of destroying the Academy by superseding her late father's position as the principal. Her plan was interrupted when she meets Fumiaki and learns of the forthcoming destruction. Despite being distrusting towards Fumiaki, they form a pact to look for the Nostradamus Key. In order to find the Nostradamus Key, time agents were provided with specially created cell phones. When a user finds an object of interest, by thinking of destroying it and taking a photo, and if the resulting image is that of a peaceful world, then the subject is the Nostradamus Key. Conversely, if the subject is not the Nostradamus Key, then the photo displays destruction. By using the phone, Maya and Fumiaki investigates occult occurrences as they occur in the town. (Source: Wikipedia)