Kenji, a high school student who works part time maintains a virtual online world called Oz. Oz avatars look cute and mostly their size is small. Basically the entire world is using Oz to function from e-mail and GPS to banking and weapons defense systems. Kenji has a crush on Natsuki, who invites him to work part time in the countryside over the summer. Kenji’s job is to act like Natsuki's fiancĂ© to please the family matriarch, who will be turning 90.
Just as Kenji is starting to get into it, he solves a strange mathematical puzzle that arrives to his cell phone around midnight. This turns to be the security code for Oz, and once it is cracked a mega A.I. virus called Love Machine starts unleashing hell on Oz, enslaving other avatars and using the online infrastructure to throw the real world into utter chaos. Traffic lights cease to function, people don’t know where their locations, and even plan to destroy the whole town. At Morning, news reported him as the criminal but actually he is innocent. Kenji avatar been stolen and unable to login into his account, that is when he is heading to next room to lent computer and realize that actually she is controlling “King Kazuma”, which was once very famous and always get rid all evils who trying to bring chaos to Oz.
Just as Kenji is starting to get into it, he solves a strange mathematical puzzle that arrives to his cell phone around midnight. This turns to be the security code for Oz, and once it is cracked a mega A.I. virus called Love Machine starts unleashing hell on Oz, enslaving other avatars and using the online infrastructure to throw the real world into utter chaos. Traffic lights cease to function, people don’t know where their locations, and even plan to destroy the whole town. At Morning, news reported him as the criminal but actually he is innocent. Kenji avatar been stolen and unable to login into his account, that is when he is heading to next room to lent computer and realize that actually she is controlling “King Kazuma”, which was once very famous and always get rid all evils who trying to bring chaos to Oz.
Natsuki's grandmother dies, but the family comes together to reconcile and defeat the virus. Natsuki uses her avatar to gamble at hanafuda cards, at first Natsuki is losing but because Oz is global and other countries trust her that she can bring peace to Oz, so they decided to give Natsuki a hand and win accounts back from the Love Machine, which weakens him enough so that her cousin "King" Kazuma can lay the smack down. Kenji cracks the security code and redirects a missile headed for the house - with the help of Wabisuke, the black sheep of the family who went to America and programmed Love Machine to prove he wasn't a screw up. Admittedly, it is a bit of a stretch that all these talented folks are under the same roof, but you just have to suspend disbelief.
Kenji and Natsuki say it for us, "She is amazing." The death of grandma solidifies the family, and they go after Love Machine with a vengeance. This includes his creator, Wabisuke, an unfilial son, but one that loved the old lady, who adopted him as a child knowing he was her husband's. There’s a flashback is grandma walking with the child Wabisuke hand and hand down a country road; we see them from behind walking away from us. There’s few great scenes have all the members of the family of all ages using computers, cell phones, Nintendo DS units and so on to access Oz and fight together. This isn't just about a breakdown between "the virtual" and "reality," but rather a nuanced commentary on how the virtual can affect us.
People aren't coming together, but rather being driven apart by unstable work, which strains family and dating relations. The movie is touching not because of its specific nostalgia, but rather a universal desire for a place to be and people to share it with. In Hosoda's Nagano, everyone grows up, comes together and succeeds. In scenes where the family is cheering one another on, it is hard not to join them; I almost shed a tear when Oz users from around the world offered up their avatars so that Natsuki would be able to bet enough to beat Love Machine; when Natsuki cries alone after her beloved grandma's death, I wanted to reach my hand out to her like Kenji did. With Natsuki I for once wasn't attracted to a character as such.
That said, she is cute when inviting Kenji to Nagano, begging him to play along (close up on her hands grasping Kenji's), blushing over an old crush on Wabisuke or kissing the awkward Kenji in front of everyone in the finale (in a kimono).
Summer Wars is a feel good movie, as attested by hoards of fans who on the spot decided to move to Nagano.