Akari Mamiya, a first-year student from Tokyo Butei High, idolizes the S-rank Butei Aria Holmes Kanzaki and wishes to follow in her footsteps. Despite only being an inept E-rank Butei, Akari's resolve to improve remains strong. After the idea of having an Amica contract (a senior-student mentorship program) with Aria is brought up, Akari submits a request form attempting to establish said contract. Her classmates and friends do not expect Aria to accept Akari's request, mainly because of the girl's strict selection process, but to everyone's surprise, Aria gives Akari a chance through a test, which Akari miraculously passes! However, Aria will not officially make Akari her Amica until Akari meets her standards. Training under Aria will be no easy feat, as she has to concurrently manage her relationships with her friends. Will Akari have what it takes to walk down the same path as her idol?

After preventing Japan's destruction, Akira Takizawa made one final request to become the King of Japan, before he erased his memories once again and disappeared. Leaving Saki Morimi with his cellphone, the only clue she has in regards to Akira's whereabouts is the message, I'll be waiting where our journey started. Six months later, rumors have spread about Akira, and Saki's search leads her to New York City. However, Saki is not the only person who goes to investigate—with several billion yen burning a hole in their pockets and a challenge to save Japan, the remaining Seleção are not far behind. Some are willing to help Akira achieve his goals, but a few are making dangerous moves in order to eliminate him and achieve their own picture of a better Japan. With rising stakes and new revelations, the game is still on.

On November 22, 2010, Japan was hit by missile strikes, a terrorist act that fortunately did not harm anyone, becoming known as Careless Monday. Quickly forgotten, society goes on about their lives as normal. During her graduation trip to America three months later, friendly college student Saki Morimi's life is forever changed when she finds herself saved from unexpected trouble by Akira Takizawa. Takizawa is cheerful, but odd in many ways—he is stark naked and suffers from amnesia, believing himself to be a terrorist. In addition, he possesses a strange cell phone loaded with 8.2 billion yen in digital cash. Despite Takizawa's suspicious traits, Saki quickly befriends the enigmatic young man. However, unbeknownst to her, this is the beginning of a thrilling death game involving money, cell phones, and the salvation of the world. Higashi no Eden chronicles Saki's struggle to unravel the mysteries behind her savior, while Takizawa himself battles other individuals armed with similar cell phones and returning memories which reveal his possible connection to the event from months ago.

As one of the 12 Seleção that needs to save the country in order to win a game, Akira Takizawa decided to become the King of Japan. With that in mind, after his return from the U.S.A., the remaining Seleção will also need to follow up on their own plans as they strive to outdo each other. Saki Morimi and the other members of the Eden of the East are under suspicion of being terrorists, but they still do everything they can to help Takizawa reach his goal and unravel the secrets of his past, as the last fight between the Seleção begins.