Summer Wars

Kenji Koiso, a teenage math prodigy, takes a summer job in Nagano, the hometown of Natsuki, the girl he likes. Upon arriving, he discovers that Natsuki's extended family has gathered to celebrate the 90th birthday of their grandmother. Kenji's role during the celebration is to pose as Natsuki's fiancé. At the same time, while working on a complex mathematical problem, Kenji inadvertently triggers a crisis that causes a virtual world to collide with the real world, leading to unexpected consequences.