Summer Wars S01

When shy eleventh-grader Kenji Koiso is invited by twelfth-grader Natsuki Shinohara to come with her to her family's Nagano home for a summer job, he agrees without hesitation. Natsuki's family, the Jinnouchis, have a long history dating back to the Moromachi period, and they have all gathered for the 90th birthday celebration of the energetic family matriarch, Sakae. It is there that Kenji learns his "summer job" is to pretend to be Natsuki's fiancé. While acting out this role with Natsuki, Kenji receives a strange math problem on his cell phone that, as a math prodigy, he cannot resist solving. In solving the equation, a program that can control nearly all aspects of life is hacked. Now it's up to Kenji and his "new family" to stop the hacker.