whats the premise of this show?

Jun Sakurada is a Junior High School student who refuses to go to school due to mental issues resulting from traumatic experiences there (see Hikikomori). He normally locks himself in his room and has a hobby of ordering supernatural goods online and returning them before the trial period ends and he has to pay for them. His older sister, Nori Sakurada, does everything she can to help but is unable to reach Jun.

One day, Jun receives a letter claiming he has won a prize, and asking whether or not he would "Wind" or "Not Wind". After putting the letter in his drawer as per the instructions on the letter, he receives a beautifully crafted box right after Nori comes to complain about his habits. Within is a humanoid doll wearing clothing in Victorian style. Curious, Jun winds up the doll. The doll then gets up on its own, and walks over to him and slaps him. She later on says, "My name is Shinku, the fifth doll of the Rozen Maiden." Shinku is a doll from the "Rozen Maiden" collection, and before Jun can take in what happened, Jun now holds the responsibility to protect Shinku's "Rosa Mystica" whilst they are engaged in mysterious battles with other dolls.