I'm a Behemoth, an S-Ranked Monster, but Mistaken for a Cat, I Live as an Elf Girl's Pet, Vol. 2 (light novel)

After dying in a fight against the forces of evil, a knight finds himself reincarnated as a powerful behemoth, but learns behemoth cubs look exactly like kittens, and when an elf takes him in as a pet he must apply his honor as a noble warrior to fight to protect her.