Summer Wars Complete Edition By Mamoru Hosoda

 the story of an ordinary family going to extraordinary lengths to avert the impending cyber apocalypse!
Kenji is your typical teenage misfit. He's good at math, bad with girls, and spends most of his time hanging out in the all-powerful, online community known as OZ. His second life is the only life he has - until the girl of his dreams, Natsuki, hijacks him for a starring role as a fake fiancée at her family reunion. Things only get stranger from there.