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), Paperback/Nozomi Ginyoku

As Tama continues his life as Aria's adventuring-partner-slash-pet, he one day obtains a new skill and heads to the dungeon to try it out. Once inside, he runs into a beautiful girl who's wearing nothing but rags. What could she possibly be doing there? Before Tama can find out, she tries to jump his cat bones so he runs, completely unaware of what the consequences might be...