Meet the two main characters.
I'm a Behemoth, an S-Ranked Monster, but Mistaken for a Cat, I Live as an Elf Girl's Pet (Sランクモンスターの《ベヒーモス》だけどネコと間違われてエルフ娘の騎士として暮らしています) is a Light Novel series written by Nozomi Ginyoku and illustrated by Taro Shinonome.
The story features an unnamed knight that is resurrected in a dungeon as an infant "Behemoth" monster, and picked up by the elf-girl Aria when he gets mortally wounded. After she nurses him back to health, he decides to protect and serve her, for life. In turn, she is very, very grateful.
The light novel series was first published in 2018, and a manga adaptation began serialization in Young Animal magazine that same year. The light novels and manga are both licensed in English by Yen Press.
The work includes the following tropes:
- Adaptation Explanation Extrication: Combined with Pragmatic Adaptation. The manga removes a large amount of exposition, especially in the early chapters. This reduces Tama's "fight" with various monsters to single frame panels.
- All Men Are Perverts: The entire population of "Maze City" is fixated on Aria, Tama included.
- Anatomically Impossible Sex: The main reason the main characters Can't Have Sex, Ever, unless Tama somehow picks up a shapeshifting skill of some kind.
- Aristocrats Are Evil: There's only one aristocrat on screen to date, Kassman- the only aristocrat that bothers to even take up adventuring. He loves to throw his weight around and responds with murderous rage to the merest slight, real or imagined, even ordering Tama be executed purely to force Aria and Tama to duel him, and have Aria marry him after he beats them both up.
- Bedmate Reveal: The first time Tama wakes up in Aria's home, he finds himself sandwiched in her cleavage, as she's also sleeping beside him.
- Bestiality Is Depraved: Played with. While getting impregnated by dungeon monsters is universally considered being Defiled Forever, the romantic interactions between Aria and Tama (who looks and acts like a common house-cat) are considered adorable on both sides of the fourth wall.
- Cannibalism Super Power: Most, if not all, dungeon monsters gain new powers and abilities by consuming other monsters. The MC is not exempt.
- Chainmail Bikini: It's practically a law of nature for the world that, while men can wear as much or as little armor as they want, the most coverage female armor provides still results in exposed midriffs and a Cleavage Window, with it usually being closer to a literal bikini.
- Child by Rape: Monsters, especially Goblins, are known to kidnap and capture women, then rape and impregnate them over and over again until the women die. This is explicitly lampshaded as a Fate Worse than Death.
- Dungeon-Based Economy: Maze City was built with massive walls to stop the labyrinth's monsters from swarming the world. The city prospers because adventurers go into the labyrinth dungeon to get materials that merchants use for various things, or sell in trade to other countries.
- Entertainingly Wrong: The entire population believes Tama is an Elemental Cat, not a infant Behemoth. Even if Tama could tell them the truth, he won't because adventurers would see him as a threat rather than an ally.
- First-Episode Resurrection: Close enough. Chapter 1 of the manga has "Tama" mortally wounded to wake up in Aria's home.
- Interspecies Romance: Aria an elf, and Tama a Behemoth, are completely and hopelessly entangled romantically with each other.
- Killer Rabbit: Combined with Magikarp Power. Infant Behemoths, like the MC, all have the appearance of typical house-cats, and act like them, for the most part, but if they manage to grow to adulthood are the most powerful and vicious monsters on the planet. Even as infants, they have inherent abilities that make them dangerous to the unwary.
- Pet Monstrosity: Unintended by Aria, but she does take an infant Behemoth as a pet.
- Property of Love: Tama is content being Aria's "pet," calls her "master" in his mind, and is completely devoted to her.
- Reincarnation: Tama was a human male knight before the story starts. The story begins with him being reincarnated into an infant "Behemoth" body.
- Shout-Out: Intentionally or not, the idea of a Behemoth resembling a cat, of all things, gives some vibes of The Master and Margarita.
- World of Buxom: All the females in the series are quite well endowed. Aria has the biggest breasts though, which Tama appreciates.
