I wrote something similar like this back in 7th grade. Guy saves his pet cat, cat turns into a girl..... But here's the plot: The guy died at the accident, so the cat (with the help of Nekomata), gave her 8 lives for him. The Gods did not like this because he wasn't supposed to be blessed, so they asked all animals to hunt him down. Now having cat lives meant the guy can move from the tangent human world to the spirit (animal) world. It also means conversing with animals is possible, so everyone finds him creepy and weird after the accident. The guy gets sent to the countryside in hopes for recovery, only to be met with more killer animals who, whenever he unwillingly trespasses into the spirit animal world, can also transform into humans due to the "bug" between the boundaries. The only way he can escape this fate is to seek for the Great elusive Nekomata (to summon the ritual, return the lives, and let the guy die) or he gets killed first and be punished eternally (won't get reincarnated). By the way, if he only returned 7 lives, he must sacrifice another one's life in exchange....... And if you noticed, yes, I was inspired by "The Cat Returns".