I will just assume you've misread my post since I clearly stated my situation.
Oh god damnit, I think I get it.
Ok, the whole 'situation' is that you are heading to the supermarket to buy a cure for the Rabbit's Milk Poisoning, which would turn you into a rabbit and eventually kill you. So you gotta buy that cure which is in the supermarket. So yeah, you can talk to the cats when you first get there, but nothing should happen.
Go inside the store, buy the cheap drink that cures you (I forgot what it is called) and you should automatically use it when you close the shop menu. Then when you try to go back the gate is locked. Turns out the cats locked the gate and have the key, or something. AND THEN everything should happen according to the guide.
Edit: Yeah, what the guy below said as well. That said, it sounds like you are playing according to the guide itself, and not really reading the story and etc, (like, it sounds like you talked to the cats, talked to the shop keeper, and stopped COMPLETELY which means you didn't realize you needed to cure your poisoning -> not really following the story because that's the whole reason you went to the supermarket in the first place) which probably is going to spoil your enjoyment of the game.