I remember MC start as a villager, so maybe not a reincarnation. He is a farmer and has bull (i remember its colour is green) which he call big brother. One day MC found out the bull can talk and he teach MC cultivations technique Turn out what he practice is a bull demon cultivation and MC become bull demon. He must practice it with a turtle demon cultivation so he can mimic human form again. The bull teach many cultivations technique with different monster/yao/demon (other is phoenix, monkey, etc i havent finish it). He promise his bull to meet him in upper realm He has a little girl ghost companion. The bull also teach her a buddhist cultivations technique. Later other found out about her and called her "reverse buddha" (name may vary since i dont remember if i read mtl or not) It is harem, from last i read the ghost isnt his lover. she has no feeling i think