Yaritsukai to, Kuroneko.

A man named Kagari Shuuya is placed in a white room and given the option to reincarnate in another world using a futuristic interface. He selects a half-vampire race, which resembles humans but has vampire traits and a weakness to light magic. He chooses an extra skill that lets him use light magic, creating a new hybrid species called Seivalt. His other skills are Language Comprehension, Chain Projection, and Growth Modifier. He is transported to a harsh underground world where survival is difficult despite his abilities. After months of isolation and facing deadly creatures, he encounters a large winged beast that severely injures him. He reaches an altar with a black tiger statue, where he is nearly killed but his vampiric blood alters the beast. After his body reforms into a small black cat, he continues his journey with this feline companion.