When timid eleventh-grader and math genius Kenji Koiso is asked by older student and secret crush Natsuki to come with her to her family’s Nagano home for a summer job, he agrees without hesitation. Natsuki’s family, the Jinnouchi clan, dates back to the Muromachi era, and they’ve all come together to celebrate the 90th birthday of the spunky matriarch of the family, Sakae. That’s when Kenji discovers his “summer job” is to pretend to be Natsuki’s fiancé and dance with her at the birthday celebration. As Kenji attempts to keep up with Natsuki’s act around her family, he receives a strange math problem on his cell phone which, being a math genius, he can’t resist solving. As it turns out, the solution to the mysterious equation causes a hijacking of the social networking site through which most of the world's social and business traffic flows.
This has to be a must see. Its just all around well done. The story has several interests going on that all nicely tie together so it doesn't feel like its all over the place. There are a lot of characters in it but minor or major you get a nice feel for them depending on their role and its easy to get attached to the events taking place. It's pretty long at 2 hours for an anime movie but I never once lost interest. The summary may seem odd but once you start watching it it is easy to get what's going on. Highly recommend checking this out.