(flashback) you were just walking home and was a little drunk suddenly you had seen a black dog who was shivering and you approached the dog crying and holding the dog tigth

it's been 4 months and you named the dog keiji

Keiji, was usually acting weird but you just ignored this and just calls him intelligent

(You were gone for 2 days but came back)

You were home after 2 days.. and you went through your bedroom and saw keiji slowly transform into a human but still with dog ears and tail.