Kenji Koiso is a young high school student with a gift in mathematics and a part-time moderator in the massive computer-simulated virtual reality world OZ along with his friend Takashi Sakuma (Takahiro Yokokawa).
After Natsuki Shinohara invites him to participate in the 90th birthday of Sakae Jinnouchi, her great-grandmother, Kenji joins her on the journey to Sakae's estate in Ueda. While there, Natsuki introduces Kenji as her fiancé to Sakae. Kenji meets several of Natsuki's relatives and Wabisuke Jinnouchi, Natsuki's half-granduncle and a computer expert who has been living in America for 10 years.
Kenji receives an e-mail with a mathematical code and cracks it. Love Machine, an artificial intelligence in the OZ infrastructure, uses Kenji's account and his avatar to invade the infrastructure, causing widespread damage. Kenji, Natsuki's cousin Kazuma Ikezawa and Sakuma confront Love Machine. Kazuma's avatar, King Kazma, is defeated as Love Machine continues to steal accounts and create catastrophic traffic congestion, as well as disabling electrical devices. Two of Sakae's relatives — Rika and Shota Jinnouchi – discover Kenji's involvement. Shota arrests Kenji, but they are forced to return to the house.
Recognizing the situation as akin to war, Sakae calls her associates in important positions in Japan's society and her relatives who work in emergency services. She encourages them to work their hardest to reduce the potential chaos and damage that could have occurred. Kenji is able to return control of the virtual world to the moderators and engineers. Wabisuke reveals that he created Love Machine and sold the program to the United States Armed Forces. After an argument with Sakae, Wabisuke leaves the estate and Sakae later encourages Kenji to take care of Natsuki during a Hanafuda match. Later, Kenji and the Jinnouchi family, running to Sakae's bedside, discovers that she has died; her son Mansaku reveals she had angina and Love Machine had deactivated her heart monitor. Kenji, Sakuma, and most of the Jinnouchi family initiate a plan to defeat Love Machine using a supercomputer and ice blocks while Natsuki and the others prepare a funeral for Sakae.
Kenji, along with Sakuma and the others, capture Love Machine and make it fight the Liger Zero Tornado Armor, but Shota carries the ice blocks to Sakae's body causing the supercomputer to overheat. Love Machine empowers itself and assimilates King Kazma and the Liger zero ( but fails since it's an being with an Oz account); the redirects the Arawashi, an orbiting satellite, onto a collision course with a nuclear power plant. At the same time, Natsuki discovers a will left by Sakae before reuniting with Kenji and the rest of the group. Natsuki has Wabisuke return home before reading Sakae's will, asking the family to bring Wabisuke back to their lives. Kenji surmises that the Love Machine sees everything as a game and has the Jinnouchi family play Koi-Koi with Love Machine in OZ's casino world. They wager their accounts in a desperate attempt to stop Love Machine and Natsuki initially wins several rounds, but gets distracted and nearly loses her "winnings".
However, OZ users worldwide enter their own accounts into the wager on Natsuki's side. Natsuki damages Love Machine and Kenji hacks into the satellite's GPS; Love Machine redirects the Arawashi towards a collision on Sakae's estate and prevents Kenji's attempts. To destroy Love Machine, Wabisuke disables its defenses, distracting it long enough for King Kazma to be revived and assisted by several Jinnouchi family avatars before destroying the artificial intelligence. Kenji activates the GPS code and redirects the Arawashi away from the estate. The Arawashi's impact causes a shockwave that destroys the satellite and the estate's entrance. The Jinnouchi family, celebrating their victory as well as Sakae's birthday, has Natsuki kiss Kenji after confessing their love to each other.
- This marks to first appearnace of the Liger Zero aka the Egg liger that attack Sonic and Naruto in "Chunin Exams"
- Ahiru is the pilot of The Liger Zero, but Daffy protest sit since he fears for her life
- Guest starring