The zombie girl 01 is his sister. she gives the direction in which she is heading in relation to where she left the message.Another thing that doesn't make sense. These "blood stains" stop you while you walk (red square), who knows for what physical reason and these don't (green square) .
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Bloodstains are programmed to appear in certain places and this stain should normally be on a wall. That's why you can't step on it.
PS: There is an error in one of the messages, It is the pond that is to the south and not to the north of the store.