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

Reincarnation is the cat's meow!

Aria and Tama's party is getting a new member -- a tanned girl with tiger ears and an enormous war hammer?! Thanks to her help, their days of carefree dungeon crawling are going better than ever, as Aria strives to overcome her weaknesses and Tama learns some...unusual skills. But that all may change when the kingdom's knights come bearing news of a dangerous quest...