Following a peculiar incident known as 'Careless Monday,' where Japan narrowly escaped harm from missile attacks, society resumes its routine without much thought. During a trip to America after the event, college student Saki Morimi encounters Akira Takizawa, a cheerful yet amnesiac young man who believes he is a terrorist and possesses a mysterious phone loaded with a massive amount of digital cash. Despite the odd circumstances, Saki forms a fast friendship with Takizawa, unaware that this marks the start of a high-stakes game involving money, phones, and the fate of the world. As Saki delves into uncovering the truth behind Takizawa, he grapples with his own past and potential ties to the earlier incident, engaging in a gripping battle against others wielding similar phones and resurfacing memories.