Smartphone apps are used by everyone worldwide. However, within these applications dwell enigmatic entities known as "Appli Monsters," or "Appmon." These AI beings possess cognitive abilities and inhabit the interface between the digital realm and human world to facilitate communication and operation. In the boundless expanse of the internet, a powerful virus-infected "last boss AI" named Leviathan seizes control over the Appmon, initiating cyber attacks that threaten to dominate the realms of both mankind and cyberspace.
The protagonist, Haru Shinkai, embarks on a quest to harness the power of the Appli Drive, which enables him to manifest Gacchimon, an app monster for search purposes. Within this device lies a concealed secret waiting to be unraveled. What is the mysterious field that bridges the gap between the digital and physical worlds? How does the "App Combine" function, allowing two Appmons to merge into one formidable entity? And what drives Leviathan's relentless pursuit of control over humanity and the digital sphere?