Genzō Shibata, also known as the wrestler Animal Mask (Kemonā Masuku), achieved significant success in Earth's professional wrestling circuit. His primary motivation was a lifelong dream to open a pet shop, sharing his profound affection for animals. He accumulated funds through wrestling, culminating in a scheduled World Championship title match. During this pivotal event, Princess Altena Edgardo Ratis summoned him to a fantasy world, tasking him with eliminating demonic beasts. Rooted in his unwavering love for animals, he refused immediately, delivering a German suplex to the princess that exposed her underwear and earned her the enduring nickname "Princess Buttocks".

Escaping the castle, Genzō found himself stranded in the new world with his loyal pet dog, Hiroyuki. Determined to pursue his dream despite displacement, he decided to establish a pet shop specializing in magical beasts. He adopted the "beast hunter" profession through the local guild but radically diverged from expectations; instead of killing creatures, he focused on non-lethally subduing, taming, and befriending them. His goal was demonstrating harmonious human-beast coexistence and promoting pet ownership.

Physically, Genzō possesses a tall, exceptionally muscular build, short black hair, and eyes typically obscured by a fringe covering his right eye. His everyday attire is a green shirt and black pants. As Animal Mask, he dons a distinctive costume featuring a dog mask, spandex shorts, a cape, and laced boots, frequently causing others to mistake him for a pervert or exhibitionist.

His personality is defined by an intense, all-consuming love for animals bordering on obsession, manifesting as a desire for an "animal harem" and a compulsion to adopt every creature encountered. He exhibits a fetishistic attraction to animal traits like ears and tails, leading him to pet or cuddle beast-people without consent—actions perceived as perverted harassment. This fixation overrides social norms and human concerns; he displays consistent bystander syndrome regarding human conflicts, intervening only incidentally while pursuing beasts. He reacts with extreme violence—employing professional wrestling moves—to perceived threats against animals, such as witnessing weapons drawn against beasts, hearing intentions to harm them, encountering the moniker "Demon Beast Killer" applied to himself, or facing attempts to kidnap Hiroyuki. His wrestling background instilled a strong sense of pride and adherence to wrestling rules during combat, refusing weapons and valuing honorable matches, as seen when he wrestled the Orc King to resolve a conflict non-lethally.

Despite his often brutish and single-minded nature, Genzō possesses unexpected depth in animal handling. He demonstrates extensive zoological knowledge and exceptional taming abilities, befriending notoriously dangerous creatures like Cerberus packs or Manticores. His physical prowess is extraordinary: peak human strength, speed, and endurance allow him to overpower formidable opponents, including vampires, half-dragons, and demon beasts. His combat style relies exclusively on professional wrestling techniques, reflecting his indomitable fighting spirit.

He established the pet shop "Kemono Michi" and assembled a core group of companions. Shigure, a wolf-girl he rescued from slavery, manages finances and business operations, forming a brains-and-brawn dynamic. Hanako (Lindabrea Fafnir Gildmerag), a half-dragon girl with an insatiable appetite and immense strength, joined seeking new culinary experiences. Carmilla Vanstein, Hanako's vampire maid, reluctantly followed her mistress; despite arrogance and uselessness in practical matters, she remains obsessively devoted to Hanako. A mysterious giant ant named Jeeg joined, performing housekeeping duties. Genzō's relationship with these companions is pragmatic, centered on supporting his pet shop venture, though he remains oblivious to Carmilla's disdain and Hanako's true draconic nature.

His presence significantly impacted the world. Consistent success pacifying dangerous beasts earned him the unwanted title "Demon Beast Killer" among adventurers and townsfolk, a label he vehemently rejects. His actions inadvertently escalated tensions; his wrestling rival, Macadamian Ogre (MAO), was later summoned by vampire princess Joanna to serve as the opposing faction's champion, eventually becoming the Demon King. Princess Altena pursued him relentlessly, initially seeking revenge for her humiliation, though repeated defeats in wrestling matches reportedly led her to develop masochistic tendencies.

Genzō faced supernatural challenges. Princess Altena cast a spell nearly eradicating his passion for animals, later lifted by Joanna, restoring his fervor with heightened intensity. He also suffered a curse from Carmilla Vanstein causing him to lose hair every time he sneezed.

Throughout his journey, Genzō remained steadfastly dedicated to operating a pet shop where humans and magical beasts could connect. His methods—blending non-lethal wrestling combat with genuine animal empathy—challenged the world's established view of beasts as solely threats to be exterminated. His story chronicles efforts to capture, tame, and find suitable homes for creatures while navigating financial struggles, societal misunderstandings, and conflicts arising from his unique perspective and formidable abilities.