Aria, a beautiful elven adventurer, never expected her journey to change with one small encounter. When an adorable little beast clings to her ample chest, she decides to keep it as a pet and lovingly names it “Tama.” At first glance, Tama appears to be nothing more than a cute, ordinary cat. But what Aria doesn’t realize is that her new companion is hiding a shocking secret—Tama is actually a former knight, reborn as a young Behemoth, the most powerful monster class of all. What begins as a lighthearted bond between elf and pet soon unravels into a fantasy adventure filled with mystery, hidden identities, and the unstoppable power of the strongest monster.