Killer Rabbit!

Nohara Asuka is an ANBU agent and one of the last members of the Nohara clan. He's always felt like everyone looks straight past him to see the living ghost of his dead aunt. One day, after an especially demeaning mission, he wakes up in a cave surrounded by weirdos, whose leader keeps calling him Rin, and realizes there's only one way to survive. Becoming one of them.