After their loss against Suzuridani Academy, the members of the Keishin Academy girls' basketball team—Tomoka Minato, Maho Misawa, Airi Kashii, Hinata Hakamada, and Saki Nagatsuka, along with their coach, Subaru Hasegawa—exert more of their time and effort in improving in the sport day by day. However, this time around, new rivals with strengths possibly exceedings theirs and friends appear on their way to the top.

Ro-Kyu-Bu! OVA bundled with the PlayStation Portable game Ro-Kyu-Bu!: Himitsu no Otoshimono.

During the events of the original Rozen Maiden, after circling yes on a paper and agreeing to wind an unknown something, a traumatized Jun Sakurada fights alongside the lifelike dolls known as the Rozen Maidens. But what would have happened if Jun had circled no? Jun, having gotten over his school trauma from his younger days, spends his time attending college and working in a bookstore. However, he does not feel as though he belongs anywhere. One day, he finds a book containing instructions on how to make a Rozen Maiden. Mysteriously, when he arrives home that night, the second volume in the book series has been delivered to his house, along with some pieces of a doll. But as suddenly as they started arriving, the books stop coming, and Jun gets a notice that says that the books have ceased being published. With an incomplete doll in hand, and a message from his other self in another world, this Jun also finds his way into the world of the Rozen Maidens.

During the turbulent end of the Tokugawa era, many children became war orphans. One of these orphans, a nameless son of a samurai, ends up meeting Ryouma Sakamoto, a man working against the Bakufu government. Impressed by the orphan's skill with a blade, Ryouma gives him the name Ryo and lets him travel by his side.