SUMMER WARS (MamoruHosoda, 2009)
Timid eleventh grader and math genius Kenji Koiso is asked by his secret crush Natsuki to come with her to her family's Nagano home for a summer job. Turns out, Kenji discovers, his "summer job" is to pretend to be Natsuki's fiancé for the celebration of her spunky grandmother's 90th birthday. While there, he receives a strange math problem on his cell phone, and, being a math genius, he can't resist solving it. However, his solution creates chaos within the virtual world of OZ, translating into anarchy in real life.