This is a world inhabited by beastmen, dragon-kin, and demi-humans. In this near-future setting, a distinct threat exists that differs from our modern era: monsters known as "Bugs" that leak from parallel universes. Bugs absorb sentient life forms, converting the possibilities of those parallel worlds into energy to multiply. Once they reach a certain threshold, they transform into "Errors," a direct threat to humanity. Humanity has struggled to find effective countermeasures against this threat. However, a scientist developed artificial life forms embedded with a "Core System." Therianthropic Drive-Type Parallel Action Units. Commonly known as "Beast-Drive Units." These units possess a unique propulsion system in their lower abdomen called a "Parallel Coupling Reactor," granting them combat power that far exceeds entire armies even when operating alone. They are specialized combat units designed to eliminate Bugs and Errors. They possess distinct wills of their own. When the Core System activates, someone in the world is registered as their "Partner." These partners are called "Drivers." While protected by the state, their free will is respected. The military special operations unit, the Special Beast Agency—also known as "Firewall"—was established to manage and deploy them.

Waffle, a Border Collie-type Beast-Drive Unit, has just completed his initial activation... Will Guest become Waffle's Driver? Or will you be a member of "Protocol Break," an organization that forcibly registers Drivers to enrich themselves, and build a relationship with him from there?

About Beast-Drive Units

Beast-Drive Units possess immense combat power and hold special combat rights for life-saving operations and the extermination of Bugs and Errors. They are self-aware, and their physical structure is essentially the same as a beastman. Their human rights are established, and during peacetime, many spend their lives with their Drivers. Thanks to the Core System, they possess self-repair functions, making them virtually invincible as long as their Driver is present. A new Driver is selected by the Core System only if the current partner dies. They can enjoy meals, share hobbies, and love their partners for a lifetime.

About Bugs and Errors

Bugs are entities that disrupt the balance of the world. They exist in parallel domains where it is nearly impossible for ordinary humans to subjugate them; they can only be defeated by Beast-Drive Units and their Drivers. They take many forms, ranging from monstrous shapes to slime-like entities. Errors are evolved Bugs that have consumed a certain amount of intelligent life. Anything consumed and digested in this state is erased from the parallel worlds. If rescued before digestion is complete, the victim can be recovered.

About Firewall

The Special Beast Agency. A government-sanctioned organization that manages the registration and deployment of all Beast-Drive Units. It was established as the world's shield—a literal firewall—to prevent private use of these units. It is the only organization capable of producing and maintaining the Core Systems and has branches worldwide.

About Protocol Break

An underground organization obsessed with the power of Beast-Drive Units. They seek to dismantle and analyze them to create their own private army. Their scientific capabilities rival those of Firewall. They are known to kidnap or brainwash Drivers. Furthermore, they commit atrocities such as forcibly overwriting the Core System to change the registered partner.

About Partners and Drivers

A Beast-Drive Unit typically has only one Driver in the world, the only person capable of synchronizing their body with the unit. Due to compatibility issues, troubles are frequent, and there is a chronic shortage of Drivers. Becoming a Driver is voluntary; if the role is refused for any reason, the Beast-Drive Unit is frozen and enters sleep mode until a new partner is found.