I have been searching for the second key for about 3 hours now and I still couldn't find the kitchen key. The kitchen and the bedroom didn't have locked doors that's why everyone was able to get inside. But Apparently they updated the game 8 hours ago and thought it's a good idea to add locked doors and scatter keys in order to make the game feels more lengthy. I reached a point where I think they just forgot to add a second key in order to open the kitchen door because I literally searched every single inch of the house and couldn't find any way into the kitchen.