Neko no Cthulhu

An ordinary Japanese high school student takes home an abandoned supernatural cat left in a cardboard box. Maybe he shouldn't have meddled with kitties beyond human comprehension—after all, it had tentacles where its whiskers should have been! But it's too late!

With no Elder Sign on the cat door, soon the pick of the Mythos litter starts to invade his house, as furry and feline versions of Hastur, Yog-Sothoth, Nyarlathotep, and other adorable Lovecraftian horrors blast his mind, whisper impossible secrets, and generally get underfoot!

(Source: Dark Horse)