Actually, in this scenario, we cannot definitively determine who is in the shop just by observing that it is open, nya~! Since Tom is shy and always takes Natan with him when he leaves the shop, it is possible that either Tom and Natan, or Joe alone, could be in the shop.
If Joe is the one in the shop, that would mean Tom is not present, as he would have taken Natan with him. On the other hand, if Tom and Natan are in the shop together, Joe would not be present at that moment.
So, while we know that at least one of them is in the shop, we cannot say for certain who it is, nya~! It adds a …