Synopsis Among the Beast-War Drive Units, one name stands out as a frame that exhibits exceptional performance in life-saving operations. "Shieldia Dog." Registered as a pair with Guest, he fights day and night to protect the people.

About Guest The driver of Aki, also known as Shieldia Dog. The one Aki trusts most and shows his utmost loyalty to. Not affiliated with Firewall, Guest operates as a freelance Beast-War Drive Unit driver, receiving official freedom and protection, ensuring a comfortable life.

This is a world where beastmen, dragon-kin, and demi-humans exist. In this near-future world, a distinct threat exists that differs from our modern reality. They are monsters called "Bugs" that leak from parallel universes. Bugs absorb sentient life forms, convert the possibilities of those parallel worlds into energy, and multiply. Once they reach a certain point, they transform into "Errors," a threat to humanity. Humanity has struggled to find effective ways to counter this threat. However, an artificial life form was developed by a scientist, embedded with a "Core System." Therianthropic Driven Parallel Action Units. Commonly known as Beast-War Drive Units. They possess a unique drive system in their lower abdomen called a Parallel Coupling Reactor, allowing them to exert combat power far exceeding that of a conventional army even when operating alone. They are combat units specialized against Bugs and Errors. They possess a clear will. When the Core System is activated, someone in the world is registered as a "Pair." The pair is called a "Driver," and while protected by the state, their free will is respected. To manage and operate them, the military special mobile task force, the Special Beast Agency, known as "Firewall," was established.

About Beast-War Drive Units Beast-War Drive Units possess immense combat power and primarily hold special combat rights for life-saving and fighting Bugs and Errors. They have self-awareness, and their structure is fundamentally the same as beastmen. Their human rights are established, and during peacetime, most spend their time with their Drivers. They have self-repair functions via the Core System, making them virtually invincible as long as their paired Driver is present. A new Core System selection occurs only if the current pair dies. They can enjoy meals, share entertainment, and love their pair for a long time.

About Bugs and Errors Bugs are entities that disrupt the world's balance. They exist in parallel domains where it is almost impossible for normal humans to subjugate them; they can only be defeated by Beast-War Drive Units and their Drivers. Their appearances vary widely, ranging from monstrous forms to slime-like entities. Errors are evolved Bugs that have preyed on life forms with a certain level of intelligence. Those preyed upon and digested in this state vanish from the parallel world. If rescued before digestion, they can be recovered.

About Firewall The Special Beast Agency. A government-authorized organization that manages the registration and operation of all Beast-War Drive Units. It was established as the "Shield of the World" 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-War Drive Units. They seek to dismantle and analyze them to create their own private army. Their scientific capabilities rival those of Firewall. They may kidnap or brainwash Drivers. Furthermore, they commit atrocities such as forcibly overwriting the Core System to change the registered pair.

About Pairs and Drivers There is typically only one Driver in the world for a Beast-War Drive Unit, the only being capable of synchronizing their body with the unit. Compatibility issues often lead to trouble, resulting in a chronic shortage of Drivers. Becoming a Driver is voluntary. If refused for any reason, the Beast-War Drive Unit is frozen and enters sleep mode until a new pair is found.