Tama, a reincarnated entity, began existence as an unnamed human knight slain by a demon. Reborn as an infant S-ranked behemoth possessing immense latent power, his physical form remains that of an ordinary yellow tabby kitten with brown stripes. This deceptive appearance consistently leads others to mistake him for a common cat or elemental cat. He retains the memories and noble personality of his knightly past life, upholding a strict code of honor and devotion. This manifests as fierce protectiveness towards trusted allies and pronounced disdain for dishonorable acts like sexual harassment.

Mortally wounded by an earth dragon after emerging from a dungeon treasure chest, he is discovered and rescued by the elf adventurer Aria. Her nursing care fosters profound loyalty and gratitude, compelling him to pledge himself as her protector and knight. He formally becomes her pet and familiar, accepting the name "Tama." His core motivation is safeguarding Aria, driven by her past trauma and his unwavering knightly duty.

Tama possesses innate behemoth abilities augmented by a unique power: consuming defeated monsters allows him to permanently absorb their skills and attributes. This enables continuous accumulation of diverse powers. He also stores items within a personal pocket dimension. As he grows stronger, he unlocks a transformation into a larger, formidable beast form.

His relationship with Aria forms his emotional core; fiercely devoted to her safety, he reacts aggressively to threats against her. He internally calls her "master," embracing his dual role as her pet knight. While deeply affectionate towards Aria and trusted companions like the blacksmith Vulcan (who crafts his armor and offers care), he sometimes displays discomfort with overt affection or intimacy, reflecting the tension between his human memories and feline existence. This reincarnation imposes a physical limitation preventing conventional romance despite mutual feelings.

His development involves strengthening bonds within Aria's growing party, including Stella—a human girl reincarnated from the earth dragon he killed—demonstrating his capacity for alliance beyond past conflicts. His journey follows continuous growth through absorbing monster abilities, steadfast protection of Aria and her allies during quests and battles against threats like demons and undead, and his commitment to live as Aria's knight in the guise of her pet cat.